Implant with Elastomeric Membrane and Methods of Fabrication Thereof

ABSTRACT

A method of forming an implant includes providing a preformed shell formed from at least one cured elastomeric layer. The preformed shell includes an outer surface, an inner surface, and an opening for accessing an interior volume of the preformed shell. The method further includes expanding the preformed shell to an expanded state, in which the interior volume is greater than the interior volume of the preformed shell at a time of forming the preformed shell and forming an inner zone having at least one inner elastomeric layer on at least a portion of the inner surface of the preformed shell, while the shell is in the expanded state, thereby forming a multi-zone shell. The method further includes reducing the interior volume of the multi-zone shell, thereby contracting the at least one inner elastomeric layer of the inner zone and causing texturing of the at least one inner elastomeric layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 15/133,651, filed Apr. 20, 2016, which is a divisional of U.S.patent application Ser. No. 14/079,180, filed Nov. 13, 2013, whichissued as U.S. Pat. No. 9,351,824 on May 31, 2016, which claims priorityto U.S. Provisional Patent Application No. 61/726,198, filed Nov. 14,2012, each of which is hereby incorporated by reference in its entirety.

Also, this application is also a continuation-in-part of InternationalPatent Application No. PCT/US2017/028810, filed Apr. 21, 2017, whichclaims priority to U.S Provisional Patent Application No. 62/420,134filed Nov. 10, 2016, and U.S. Provisional Patent Application No.62/325,714 filed Apr. 21, 2016, each of which is hereby incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

This invention generally relates to implant prosthetics and methods offabrication thereof and, in particular, to implants having anelastomeric membrane or shell with textured inner and/or outer surfaces.

Description of Related Art

Many breast implants are commercially available. A single chamber designis most common and is available in a variety of fixed volumes to producea range of sizes and shape characteristics from about 80 to 800 cubiccentimeters. As used herein, “chamber” refers to the interior portion ofa breast implant, which is enclosed by an outer shell or membrane. As isknown by those skilled in the art, the interior portion of an implantmay also be referred to as a lumen. Implants are generally filled withsilicone gel or saline. Viscoelastic silicone shells of implants can besimilar in composition, but vary in thickness, texture, and surfacetreatments. There are also significant differences with respect to thefilling materials. The silicone gel implants generally have more naturalproperties, with fewer noticeable edges and rippling effects. Theviscosity of the silicone gel reduces fluid motion that results in thesebeneficial properties. The silicone gel filling the implant may alterover time to become firmer, softer, and change in elasticity, dependingon its composition. Historically, a major complication has been gelbleed leading to capsular contraction and tissue toxicity to thepatient. Many gel-filled implants have additional barrier coatings orlayers to lessen the diffusion of silicone into the tissues. Diffusioncan be reduced, but not eliminated.

Saline implants were developed to eliminate complications related tofluid bleed. Saline is biocompatible and able to be absorbed withouttissue toxicity complications in the event of a slow bleed or rupture ofthe implant. The low viscosity of saline allows for significant fluidmotion leading to deformation of the fluid-filled shell. The wave andripple motion is often visible through the overlying tissue. This is amore significant complication in cases where there are not significantamounts of tissue surrounding the implant. The deformation of theviscoelastic membrane can cause the surrounding tissue to scar andcontract, distorting and hardening the feel of the implant. Salineimplants are often placed deep under muscle tissue of the chest andslightly overfilled to prevent complications.

Shell coatings and texturing have been developed to reduce capsularcontraction, with reasonable success. For example, variable surfacetreatments can work by enabling tissues to adhere and distribute forcesresponsible for contracture. The materials utilized to form, coat, andfill the implants have resulted in a wide variety of available designs.Size and shape alone produce many options. The designs become moreinvolved when multi-chamber and variable volumetric designs areconsidered. Variability of volume during surgery allows for adjustmentsto be made for general size and symmetry. Access ports and valves areused to inflate or deflate the implant. In some cases, the filling tubeis left in place for a short period to allow for further adjustmentspost-surgery. This adjustability is a desirable and, often, a necessaryfeature in the case of tissue expanders.

Multi-chamber implants predominantly consist of an inner chamber and anouter chamber filled with silicone, saline, or a combination thereof.The combination of chambers allows for greater variability in size andshape characteristics. Currently available models have a doublemembrane, double chamber design, in which an outer chamber has a fixedvolume of gel and an adjustable inner chamber is filled with saline.These implants provide a natural appearance and feel with the addedadvantage of temporary adjustability. However, these more complexdesigns have been found to be less resistant to shear forces in areaswhere there are junctions between the membranes and valve port.

An exemplary implant formed from an elastomeric shell with a texturedexterior surface is disclosed in U.S. Pat. No. 8,506,627 to Van Epps etal. The implant disclosed in the '627 patent includes a texturedfixation region on an anterior face of the shell. The fixation regioncan have a different texture from other portions of the exterior surfaceof the shell. In some examples, the shell of the implant is formed overa mandrel. For example, the mandrel can be repeatedly dipped into aflowable silicon elastomer until a membrane of desired thickness isformed. Portions of the exterior surface of the membrane can besubjected to a texturing process in which granulated solid particles(e.g., salt crystals) are applied over portions of the exterior surfaceof the membrane to form the fixation surface. After the textured surfacestabilizes, the granulated solid particles can be removed by, forexample, immersing the membrane in a fluidized bath (e.g., an aqueoussalt bath) to dissolve the particles, resulting in a membrane with atextured surface resembling a plurality of crystalline particles.

However, there is a continuing need to develop implants that safelyprovide a natural feel and appearance when surgically implanted. Forexample, implants should adhere and/or interact with breast or otherbody tissues in a biocompatible and effective manner Further, implantdesigns with improved biocompatibility and/or which can be manufacturedmore easily and efficiently are needed. The implants and methods offormation thereof provided herein are provided to address some or all ofthese needs.

SUMMARY OF THE INVENTION

According to a preferred and non-limiting embodiment or aspect, anadjustable implant is provided. The adjustable implant comprises anelastomeric membrane enclosed or partially enclosed about a chamber,which is adapted to expand when filled with a fluid. The membranecomprises: an outer zone formed from at least one outer elastomericlayer, the outer zone comprising an exterior surface having at least onemolded textured portion thereon; and an inner zone formed from at leastone elastomeric middle layer positioned on an inner surface of the outerzone. The implant is configured such that the inner zone is undercontraction from a contracting force provided by the outer zone.

According to another preferred and non-limiting embodiment or aspect, amethod of forming an implant is provided. The method comprises: formingan outer zone of an elastomeric membrane comprising at least oneelastomeric layer by casting in a mold, wherein an inner surface of themold comprises one or more textured portions, which are molded onto anexterior surface of the at least one elastomeric layer to form one ormore molded textured portions. The method further comprises: expandingthe outer zone, such that a volume enclosed by the outer zone isexpanded; forming an inner zone comprising one or more elastomericlayers in the expanded outer zone; retracting the outer zone and theinner zone to a retracted state; and forming an adjustable implant fromthe membrane by enclosing the membrane to form at least one chamber.

According to another preferred and non-limiting embodiment or aspect, animplant for volumetrically altering, replacing, expanding, or augmentingtissues is provided. The implant includes an enclosed or partiallyenclosed elastomeric membrane formed from one or more laminatedelastomeric layers. The membrane defines an interior volume. The implantalso includes a cohesive gel disposed in the interior volume of theelastomeric membrane. A volume of the cohesive gel is greater than avolume enclosed by the elastomeric membrane at the time of curing,thereby causing the elastomeric membrane to exert a contracting force onthe cohesive gel.

According to another preferred and non-limiting embodiment or aspect, amethod of forming an implant for volumetrically altering, replacing,expanding, or augmenting tissues is provided. The method includes:forming an elastomeric membrane having one or more laminated elastomericlayers, the membrane enclosing or partially enclosing an interiorvolume; expanding the elastomeric membrane, such that the interiorvolume enclosed or partially enclosed by the elastomeric membrane isexpanded; filling the elastomeric membrane with a flowable elastomericmaterial; and curing the elastomeric material to form a cohesive gel.

According to another preferred and non-limiting aspect or embodiment, amethod of forming an implant for volumetrically altering, replacing,expanding, or augmenting body tissues including an elastomeric membraneat least partially enclosing an interior volume is provided. The methodincludes: forming an outer zone of the elastomeric membrane by castingin a mold, the outer zone comprising at least one elastomeric layer,wherein an inner surface of the mold comprises one or more texturedportions, which are molded onto an exterior surface of the outer zone,thereby forming one or more molded textured portions on the exteriorsurface of the outer zone. The method further includes expanding theouter zone, thereby increasing a volume enclosed by the outer zone andforming an expanded zone of the elastomeric membrane comprising at leastone elastomeric layer on an inner surface of the outer zone. Theexpanded zone at least partially encloses a volume at the time offorming, which is greater than a volume enclosed by the outer zone atthe time of forming the outer zone. The method further includes formingan adjustable implant from the elastomeric membrane by enclosing theinterior volume, wherein the exterior surface of the implant comprisesone or more molded textured portions.

According to another preferred and non-limiting embodiment or aspect, animplant for volumetrically altering, replacing, expanding, or augmentingtissues is provided. The implant includes: an enclosed or partiallyenclosed elastomeric membrane formed from a plurality of laminatedelastomeric layers. The membrane defines an interior volume. The implantfurther includes a cohesive gel disposed in the interior volume of theelastomeric membrane. A volume of the cohesive gel is greater than avolume enclosed by the elastomeric membrane at the time of curing theelastomeric membrane, thereby causing the elastomeric membrane to exerta contracting force on the cohesive gel. An exterior surface of theelastomeric membrane comprises at least one textured portion having atexture pattern different from other portions of the exterior surface ofthe elastomeric membrane.

According to another preferred and non-limiting aspect or embodiment, amethod of forming an implant for volumetrically altering, replacing,expanding, or augmenting body tissues includes providing a preformedshell formed from at least one cured elastomeric layer. The preformedshell includes an outer surface, an inner surface, and an opening foraccessing an interior volume of the preformed shell. The method alsoincludes expanding the preformed shell to an expanded state, in whichthe interior volume is greater than the interior volume of the preformedshell at a time of forming the preformed shell, and forming an innerzone having at least one inner elastomeric layer on at least a portionof the inner surface of the preformed shell, while the shell is in theexpanded state, thereby forming a multi-zone shell. The method furtherincludes reducing the interior volume of the multi-zone shell, therebycontracting the at least one inner elastomeric layer of the inner zoneand causing texturing of the at least one inner elastomeric layer,followed by forming the implant by enclosing the multi-zone shell toform at least one chamber.

According to another preferred and non-limiting aspect or embodiment, amethod of forming an implant for volumetrically altering, replacing,expanding, or augmenting body tissues includes providing a preformedshell formed from at least one cured elastomeric layer. The preformedshell includes an outer surface, an inner surface, and an opening foraccessing an interior volume of the preformed shell. The method furtherincludes placing the preformed shell on a mandrel to expand thepreformed shell to an expanded state in which the interior volume of thepreformed shell is greater than a volume of the preformed shell at atime of forming the preformed shell. While the preformed shell is on themandrel, an outer zone having at least one outer elastomeric layer isformed on at least a portion of the outer surface of the preformedshell, while the preformed shell is in the expanded state, to form amulti-zone shell. The method further includes placing the multi-zoneshell on a mandrel in an inverted orientation, in which the outer zoneof the multi-zone shell contacts the mandrel and forming an inner zonehaving at least one inner elastomeric layer on at least a portion of aninner surface of the multi-zone shell, while the multi-zone shell is onthe mandrel and in the expanded state. Next, the method includesreducing the interior volume of the multi-zone shell by removing themulti-zone shell from the mandrel, thereby contracting the at least oneouter elastomeric layer and the at least one inner elastomeric layer.The method further includes causing texturing of the at least one outerelastomeric layer and the at least one inner elastomeric layer; andforming the implant by enclosing the shell to form at least one chamber.

According to another preferred and non-limiting aspect or embodiment, animplant for volumetrically altering, replacing, expanding, or augmentingtissues includes an enclosed or partially enclosed elastomeric shellformed from a plurality of laminated elastomeric layers defining aninterior volume; and a cohesive gel disposed in the interior volume ofthe elastomeric shell. The elastomeric shell includes: a preformed shellcomprising at least one elastomeric layer having an inner surface and anouter surface; an outer zone having at least one outer elastomeric layercovering at least a portion of the outer surface of the preformed shell;and an inner zone having at least one inner elastomeric layer coveringat least a portion of the inner surface of the preformed shell. A volumeenclosed by the outer zone and the inner zone at the time of forming theouter zone and the inner zone is greater than a volume of the preformedshell at a time of forming the preformed shell.

Further preferred and non-limiting embodiments or aspects of the presentinvention will now be described in the following numbered clauses:

Clause 1: A method of forming an implant for volumetrically altering,replacing, expanding, or augmenting body tissues comprising anelastomeric membrane at least partially enclosing an interior volume,the method comprising: forming an outer zone of the elastomeric membraneby casting in a mold, the outer zone comprising at least one elastomericlayer, wherein an inner surface of the mold comprises one or moretextured portions which are molded onto an exterior surface of the outerzone, thereby forming one or more molded textured portions on theexterior surface of the outer zone; expanding the outer zone, therebyincreasing a volume enclosed by the outer zone; forming an expanded zoneof the elastomeric membrane comprising at least one elastomeric layer onan inner surface of the outer zone, the expanded zone at least partiallyenclosing a volume at the time of forming which is greater than a volumeenclosed by the outer zone at the time of forming the outer zone; andforming an adjustable implant from the elastomeric membrane by enclosingthe interior volume, wherein the exterior surface of the implantcomprises one or more molded textured portions.

Clause 2: The method of clause 1, further comprising retracting theelastomeric membrane to a retracted state prior to forming the implantfrom the elastomeric membrane, wherein the volume enclosed by the outerzone in the retracted state is greater than the volume enclosed by theouter zone at the time of forming the outer zone, such that the moldedtextured portions of the implant are expanded compared to the one ormore textured portions of the inner surface of the mold.

Clause 3: The method of clause 1 or clause 2, wherein expanding theouter zone comprises expanding a volume enclosed by the outer zone bybetween 10% and 500% compared to the volume enclosed by the outer zonewhen formed.

Clause 4: The method of any of clauses 1-3, wherein the inner surface ofthe mold comprises at least a first molded textured portion having afirst texture pattern and at least a second molded textured portionhaving a second texture pattern, and wherein the exterior surface of theimplant comprises a portion having the first texture pattern and aportion having the second texture pattern.

Clause 5: The method of clause 4, wherein at least one of the texturedportions on the inner surface of the mold is configured to provide anadhesion region for improving adhesion with surrounding body tissues.

Clause 6: The method of clause 4 or clause 5, wherein the inner surfaceof the mold further comprises one or more substantially flat portionsseparating the textured portions.

Clause 7: The method of any of clauses 1-6, wherein forming the expandedzone comprises forming a plurality of laminated elastomeric layers ofvariable hardness.

Clause 8: The method of clause 7, wherein an innermost layer of theplurality of layers is softer than an outermost layer of the pluralityof layers.

Clause 9: The method of clause 8, wherein the innermost layer of theplurality of layers has a hardness of between about Shore 00-10 andabout Shore A-20, and wherein the outermost layer of the plurality oflayers has a hardness of between about Shore A-20 and Shore A-40.

Clause 10: The method of any of clauses 1-9, further comprisingpre-stressing the at least one elastomeric layer of the outer zone priorto expanding the outer zone.

Clause 11: The method of any of clauses 1-10, wherein forming the outerzone comprises introducing a flowable elastomeric material to the innersurface of the mold and curing the material to form the at least oneelastomeric layer.

Clause 12: The method of any of clauses 1-11, further comprising fillingthe interior volume defined by the elastomeric membrane with a flowableelastomeric material and curing the flowable elastomeric material toform a cohesive gel.

Clause 13: The method of clause 12, wherein the cohesive gel is bondedto an interior surface of the elastomeric membrane.

Clause 14: The method of clause 12, wherein a volume of the cohesive gelwhen cured is between about 5% and 50% larger than a volume enclosed bythe outer zone at the time of forming.

Clause 15: The method of any of clauses 1-14, wherein the mold comprisesa volumetrically expandable mold, and wherein an interior volume of themold is increased to cause the expansion of the at least one elastomericlayer of the outer zone.

Clause 16: The method of any of clauses 1-15, wherein the mold comprisesa plastic single-use disposable mold.

Clause 17: The method of any of clauses 1-16, wherein the at least oneelastomeric layer of the outer zone has Shore hardness of about ShoreA-10 to A-40, and preferably about Shore A-20 to Shore A-30.

Clause 18: The method of any of clauses 1-17, wherein the moldedtextured portion comprises at least one of the following: channels,ridges, protrusions, granulated or crystalline structures,cross-hatches, waves, or any combination thereof.

Clause 19: The method of any of clauses 1-18, wherein the moldedtextured portion comprises molded guidelines for assisting in surgicalplacement of the implant relative to the body tissue to be altered,expanded, or augmented.

Clause 20: An implant for volumetrically altering, replacing, expanding,or augmenting tissues, comprising: an enclosed or partially enclosedelastomeric membrane formed from a plurality of laminated elastomericlayers, the membrane defining an interior volume; and a cohesive geldisposed in the interior volume of the elastomeric membrane, wherein avolume of the cohesive gel is greater than a volume enclosed by theelastomeric membrane at the time of curing the elastomeric membrane,thereby causing the elastomeric membrane to exert a contracting force onthe cohesive gel, and wherein an exterior surface of the elastomericmembrane comprises at least one textured portion having a texturepattern different from other portions of the exterior surface of theelastomeric membrane.

Clause 21: The implant of clause 20, wherein the plurality of laminatedelastomeric layers comprise elastomeric layers of variable hardness.

Clause 22: The implant of clause 20 or clause 21, wherein an innermostlayer of the plurality of layers is softer than an outermost layer ofthe plurality of layers.

Clause 23: The implant of any of clauses 20-22, wherein the innermostlayer of the plurality of layers has a hardness of between about Shore00-10 and about Shore A-20, and wherein the outermost layer of theplurality of layers has a hardness of between about Shore A-20 and ShoreA-40.

Clause 24: The implant of any of clauses 20-23, wherein the volume ofthe cohesive gel when cured is between about 5% and about 50% largerthan a volume enclosed or partially enclosed by the elastomeric membraneat the time of curing.

Clause 25: A method of forming an implant for volumetrically altering,replacing, expanding, or augmenting body tissues, the method comprising:providing a preformed shell formed from at least one cured elastomericlayer, the preformed shell comprising an outer surface, an innersurface, and an opening for accessing an interior volume of thepreformed shell; expanding the preformed shell to an expanded state, inwhich the interior volume is greater than the interior volume of thepreformed shell at a time of forming the preformed shell; forming aninner zone comprising at least one inner elastomeric layer on at least aportion of the inner surface of the preformed shell, while the shell isin the expanded state, thereby forming a multi-zone shell; reducing theinterior volume of the multi-zone shell, thereby contracting the atleast one inner elastomeric layer of the inner zone and causingtexturing of the at least one inner elastomeric layer; and forming theimplant by enclosing the multi-zone shell to form at least one chamber.

Clause 26: The method of clause 25, wherein expanding the preformedshell to an expanded state comprises inverting the preformed shell andplacing the inverted preformed shell on a mandrel, such that the outersurface of the shell contacts a surface of the mandrel.

Clause 27: The method of clause 26, wherein a volume enclosed by thesurface of the mandrel is greater than the interior volume of thepreformed shell at the time of forming the preformed shell.

Clause 28: The method of clause 25 or clause 26, wherein reducing theinterior volume of the multi-zone shell comprises removing themulti-zone shell from the mandrel and returning the multi-zone shell toa non-inverted orientation.

Clause 29: The method of any of clauses 25-27, wherein expanding thepreformed shell comprises expanding the interior volume of the preformedshell by between 50% and 800% compared to the volume of the preformedshell at the time of forming the preformed shell.

Clause 30: The method of any of clauses 25-29, wherein forming the innerzone comprises, while the preformed shell is in the expanded state,forming a plurality of laminated inner elastomeric layers of variablehardness on the inner surface of the preformed shell.

Clause 31: The method of clause 30, wherein a proximal-most layer of theplurality of inner elastomeric layers and a distal-most layer of theplurality of inner elastomeric layers are firmer than middle layers ofthe plurality of inner elastomeric layers.

Clause 32: The method of any of clauses 25-31, wherein the proximal-mostlayer and the distal-most layer of the plurality of inner elastomericlayers are formed by blending elastomeric materials having a hardness ofup to Shore A-20, and wherein the middle layers of the plurality ofinner elastomeric layers have a hardness of between about Shore 00-10and Shore A-10.

Clause 33: The method of any of clauses 25-32, wherein forming theimplant comprising filling the interior volume of the multi-zone shellwith a flowable elastomeric material and curing the flowable elastomericmaterial to form a cohesive gel.

Clause 34: The method of clause 33, wherein the cohesive gel is bondedthe texturing of the at least one inner elastomeric layer.

Clause 35: The method of clause 34, wherein a volume of the cohesive gelwhen cured is between about 5% and 50% larger than a volume enclosed bythe preformed shell at the time of forming the preformed shell.

Clause 36: The method of any of clauses 25-35, further comprisingforming an outer zone comprising at least one outer elastomeric layercovering at least a portion of the outer surface of the preformed shell,while the preformed shell is in the expanded state and prior to formingthe inner zone.

Clause 37: The method of clause 36, further comprising reducing theinterior volume of the preformed shell after forming the outer zone,which causes texturing of the at least one outer elastomeric layer ofthe outer zone.

Clause 38: The method of clause 37, wherein the texturing of the outerzone is configured to provide an adhesion region for improving adhesionwith surrounding body tissues.

Clause 39: The method of any of clauses 36-38, wherein the outer zonecomprises a plurality of outer elastomeric layers of variable hardnessranging from about Shore 00-30 to Shore A20.

Clause 40: The method of any of clauses 36-39, wherein forming the outerzone comprises placing the preformed shell on a mandrel, such that theinner surface of the preformed shell contacts the surface of themandrel, and applying the at least one outer elastomeric layer to theouter surface of the preformed shell.

Clause 41: The method of clause 40, wherein a volume enclosed by themandrel is greater than the volume of the preformed shell, at the timeof forming the preformed shell.

Clause 42: A method of forming an implant for volumetrically altering,replacing, expanding, or augmenting body tissues, the method comprising:providing a preformed shell formed from at least one cured elastomericlayer, the preformed shell comprising an outer surface, an innersurface, and an opening for accessing an interior volume of thepreformed shell; placing the preformed shell on a mandrel to expand thepreformed shell to an expanded state in which the interior volume of thepreformed shell is greater than a volume of the preformed shell at atime of forming the preformed shell; while the preformed shell is on themandrel, forming an outer zone comprising at least one outer elastomericlayer on at least a portion of the outer surface of the preformed shell,while the preformed shell is in the expanded state, to form a multi-zoneshell; placing the multi-zone shell on a mandrel in an invertedorientation, in which the outer zone of the multi-zone shell contactsthe mandrel; forming an inner zone comprising at least one innerelastomeric layer on at least a portion of an inner surface of themulti-zone shell, while the multi-zone shell is on the mandrel and inthe expanded state; reducing the interior volume of the multi-zone shellby removing the multi-zone shell from the mandrel, thereby contractingthe at least one outer elastomeric layer and the at least one innerelastomeric layer, and causing texturing of the at least one outerelastomeric layer and the at least one inner elastomeric layer; andforming the implant by enclosing the shell to form at least one chamber.

Clause 43: An implant for volumetrically altering, replacing, expanding,or augmenting tissues, comprising: an enclosed or partially enclosedelastomeric shell formed from a plurality of laminated elastomericlayers, the elastomeric shell defining an interior volume; and acohesive gel disposed in the interior volume of the elastomeric shell,wherein the elastomeric shell comprises: a preformed shell comprising atleast one elastomeric layer, the preformed portion having an innersurface and an outer surface; an outer zone comprising at least oneouter elastomeric layer covering at least a portion of the outer surfaceof the preformed shell; and an inner zone comprising at least one innerelastomeric layer covering at least a portion of the inner surface ofthe preformed shell, wherein a volume enclosed by the outer zone and theinner zone at the time of forming the outer zone and the inner zone isgreater than a volume of the preformed shell at a time of forming thepreformed shell.

Clause 44: The implant of clause 43, wherein a volume enclosed by theouter zone and the inner zone of the implant is less than the volumeenclosed by the outer zone and the inner zone at the time of forming theouter zone and the inner zone, such that the preformed shell exerts acontracting force on the inner zone and the outer zone, which causingtexturing of the inner zone and the outer zone.

These and other features and characteristics of the present invention,as well as the methods of operation and functions of the relatedelements of structures and the combination of parts and economies ofmanufacture, will become more apparent upon consideration of thefollowing description and the appended claims with reference to theaccompanying drawings, all of which form a part of this specification,wherein like reference numerals designate corresponding parts in thevarious figures. It is to be expressly understood, however, that thedrawings are for the purpose of illustration and description only, andare not intended as a definition of the limits of the invention. As usedin the specification and the claims, the singular form of “a”, “an”, and“the” include plural referents unless the context clearly dictatesotherwise.

BRIEF DESCRIPTION OF THE DRAWINGS

Some of the advantages and features of the preferred embodiments of theinvention have been summarized herein above. These embodiments alongwith other potential embodiments of the device will become apparent tothose skilled in the art when referencing the following drawings inconjunction with the detailed descriptions as they relate to thefigures.

FIG. 1 is a sagittal view of a female human body through the left breastshowing anatomical detail along with in situ placement of an adjustableimplant according to an aspect of the disclosure;

FIG. 2 is a cross-sectional view of the adjustable implant of FIG. 1inserted in a patient's breast in a reverse orientation;

FIG. 3 is a cross-sectional view of another embodiment of an adjustableimplant according to an aspect of the disclosure;

FIG. 4 is a cross-sectional view of another embodiment of an adjustableimplant according to an aspect of the disclosure;

FIGS. 5A to 5C are photographs of textured portions of an exteriorsurface of an implant according to aspects of the disclosure;

FIG. 6 is a cross-sectional view of a casting mold for forming anelastomeric membrane according to an aspect of the disclosure;

FIG. 7 is a cross-sectional view of a portion of an elastomeric membraneformed from the mold of FIG. 6;

FIG. 8 is a cross-sectional view of an apparatus for secondary castingfor forming additional elastomeric layers on the portion of theelastomeric membrane of FIG. 7;

FIG. 9 is a cross-sectional view of the apparatus of FIG. 8 illustratinga processing step for forming an elastomeric membrane from the portionof the membrane of FIG. 7;

FIG. 10 is another cross-sectional view of the apparatus of FIG. 8illustrating a processing step for forming an elastomeric membrane fromthe portion of the membrane of FIG. 7;

FIG. 11 is a cross-sectional view of an adjustable implant formed fromthe elastomeric membrane of FIG. 10;

FIG. 12 is a cross-sectional view of another casting mold for forming anelastomeric membrane according to aspects of the disclosure;

FIG. 13 is a cross-sectional view of an apparatus for secondary castingfor forming additional elastomeric layers on the portion of theelastomeric membrane of FIG. 12;

FIG. 14 is a cross-sectional view of the apparatus of FIG. 13illustrating a processing step for forming an elastomeric membrane fromthe portion of the membrane of FIG. 12;

FIG. 15 is a cross-sectional view of another embodiment of an implantformed from the elastomeric membrane of FIG. 14;

FIG. 16 is a cross-sectional view of a casting mandrel for forming anelastomeric membrane of an adjustable implant according to an aspect ofthe disclosure;

FIG. 17 is a cross-sectional view of a portion of an elastomericmembrane formed from the mandrel of FIG. 16, during a subsequentprocessing step, according to an aspect of the disclosure;

FIG. 18 is a cross-sectional view of a portion of the elastomericmembrane of FIG. 17, during a subsequent processing step according to anaspect of the disclosure;

FIG. 19 is an adjustable implant formed from the elastomeric membrane ofFIG. 18 according to an aspect of the disclosure;

FIG. 20 is a cross-sectional view of a casting mandrel for forming anelastomeric membrane of an adjustable implant according to an aspect ofthe disclosure;

FIG. 21 is a cross-sectional view of a portion of an elastomericmembrane formed from the mandrel of FIG. 20, during a subsequentprocessing step, according to an aspect of the disclosure;

FIG. 22 is a cross-sectional view of a portion of the elastomericmembrane of FIG. 21, during a subsequent processing step according to anaspect of the disclosure;

FIG. 23 is an adjustable implant formed from the elastomeric membrane ofFIG. 22 according to an aspect of the disclosure;

FIG. 24 is a cross-sectional view of a casting mandrel for forming anelastomeric membrane of an adjustable implant according to an aspect ofthe disclosure;

FIG. 25 is a cross-sectional view of a portion of an elastomericmembrane formed from the mandrel of FIG. 24, during a subsequentprocessing step, according to an aspect of the disclosure;

FIG. 26 is a cross-sectional view of a portion of the elastomericmembrane of FIG. 25, during a subsequent processing step according to anaspect of the disclosure;

FIG. 27 is an adjustable implant formed from the elastomeric membrane ofFIG. 26 according to an aspect of the disclosure;

FIG. 28 is a cross-sectional view of an elastomeric membrane for anadjustable implant according to an aspect of the disclosure

FIG. 29 is a cross-sectional view of the elastomeric membrane of FIG. 28in an inverted position according to an aspect of the disclosure;

FIG. 30 is a cross-sectional view of an adjustable implant formed fromthe elastomeric membrane of FIG. 28 according to an aspect of thedisclosure;

FIG. 31 is a schematic cross sectional view of another exemplaryelastomeric implant according to an aspect of the disclosure;

FIGS. 32A-32E are schematic drawings illustrating an exemplary processfor forming the implant of FIG. 31 according to an aspect of the presentdisclosure;

FIGS. 33A-33E are schematic drawings illustrating an exemplary processfor forming a two-zone implant from a preformed shell, according to anaspect of the present disclosure;

FIGS. 34A-34D are schematic drawings illustrating an exemplary processfor forming a three-zone implant from a preformed shell, according to anaspect of the present disclosure;

FIGS. 35A and 35B are schematic drawings of a three-zone implant formedby the exemplary process illustrated in FIGS. 34A-34D, according to anaspect of the present disclosure;

FIG. 36A is a photograph of an inner surface of an implant shell formedaccording to the process of FIGS. 33A-33E or FIGS. 34A-34D; and

FIG. 36B is a photograph of an outer surface of an implant shell formedaccording to the process of FIGS. 34A-34D.

DESCRIPTION OF THE INVENTION

For purposes of the description hereinafter, the terms “upper”, “lower”,“right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, “lateral”,“longitudinal”, and derivatives thereof shall relate to the invention asit is oriented in the drawing figures. However, it is to be understoodthat the invention may assume alternative variations and step sequences,except where expressly specified to the contrary. It is also to beunderstood that the specific devices and processes illustrated in theattached drawings, and described in the following specification, aresimply exemplary embodiments of the invention. Hence, specificdimensions and other physical characteristics related to the embodimentsdisclosed herein are not to be considered as limiting.

For the purposes of this specification, unless otherwise indicated, allnumbers expressing quantities of ingredients, reaction conditions,dimensions, physical characteristics, and so forth used in thespecification and claims are to be understood as being modified in allinstances by the term “about.” Unless indicated to the contrary, thenumerical parameters set forth in the following specification andattached claims are approximations that can vary depending upon thedesired properties sought to be obtained by the present invention.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements.

Also, it should be understood that any numerical range recited herein isintended to include all subranges subsumed therein. For example, a rangeof “1 to 10” is intended to include any and all sub-ranges between andincluding the recited minimum value of 1 and the recited maximum valueof 10, that is, all subranges beginning with a minimum value equal to orgreater than 1 and ending with a maximum value equal to or less than 10,and all subranges in between, e.g., 1 to 6.3, or 5.5 to 10, or 2.7 to6.1.

With reference to the Figures, in general, the present disclosure isdirected to an implant 12, 112, 210 including an elastomeric membraneenclosing or partially enclosing a cavity or interior volume. Themembrane can be pre-stressed prior to filling. For example,pre-stressing can include expanding the volume of the cavitysubstantially beyond both the volume of the membrane when cured and thevolume of the finished implant. In some examples, a 500 cc membrane canbe expanded to 15 liters (e.g., an expansion of 3000%). Pre-stressingmodifies stretching and resiliency of the membrane, which is desirablein some applications. Following pre-stressing, the cavity can be filledwith a fluid, such as a biocompatible water-soluble gel, a silicone gel,or saline solution. The membrane is desirably under significantcontraction or compression. However, forces contracting the membraneshould be balanced with other forces on the membrane to produce a stableimplant 12, 112, 210. By nature of its design, the elastomeric membraneproduces a different feel than other exemplary implant membranes. Insome examples, at least a portion of the membrane can entirely enclosethe cavity. In other examples, the membrane can define an opening orhole filled by a plug (e.g., a cured elastomeric material), therebyenclosing the cavity.

The implant 12, 112, 210 of the present disclosure can be used forvarious breast reconstruction and augmentation procedures, but is notlimited to these procedures. For purposes of illustration anddescription, breast implants will be utilized as exemplary of proceduresin which the disclosed implant can be used. Variations of the inventioncan be utilized for tissue volume replacement and as a tissue expandingdevice to form tissues in post-traumatic surgery or in advance ofplanned surgery to prepare tissue flaps. As such, these implants 12,112, 210 can be employed as a permanent prosthesis or a temporarydevice, as indicated. The methods of manufacture disclosed herein can beused to produce implants with custom forms and/or material propertiesfor specific patients or procedures at an accessible cost. As such, theimplants 12, 112, 210 disclosed herein can be employed in planned,highly invasive surgeries, such as large tumor removal. For example, animplant can be fabricated in advance to replace the desired volume andform of tissues removed. As such, the implant can be utilized to beslowly expanded or contracted over time to achieve the desired shapeallowing tissues to slowly conform in a safe and predictable manner

In some preferred and non-limiting embodiments or aspects, one or morelayers or zones 18, 20, 118, 120 of the elastomeric membrane arecontinuous or substantially continuous and, preferably self-sealing.Including continuous elastomeric layers or zones enhances structuralintegrity of the implant shell, such that the implant can be filled tohigher pressures and/or expanded substantially beyond a natural volumewithout risk of rupture. Thus, in a preferred and non-limitingembodiment or aspect, the continuous and self-sealing nature of themembrane allows for adjustability (e.g., adjusting implant volume byfilling or removing fluid) without the need of special ports and fillingvalves.

In further preferred and non-limiting embodiments or aspects, an outersurface of the elastomeric membrane is textured, for example, to improveadhesion and/or interaction with breast tissue. For example, channels,ridges, or other features of a textured surface may be selected orprovided for permitting or enhancing ingrowth or adhesion of breasttissue to the exterior surface of the implant. In some examples,textured or roughened regions of an implant 12, 112, 210 can create afixation surface for adhering specific areas of the implant to breasttissue. In some examples, features of the texturing are imparted to theexterior surface of the implant during formation of the outer layers ofthe implant, for example, by casting in a mold. In particular, texturefeatures etched or otherwise produced on an inner surface of the moldare imparted to the exterior surface of the implant. The texture can bea repeating pattern across the entire external surface of the implant.In other examples, different portions of the implant surface havedifferent texture patterns to impart different interaction with bodytissue to different areas of the membrane. For example, posteriorportions of the implant 12, 112, 210 can include roughened fixationsurfaces for improved adhesion to the chest wall. In other examples,anterior portions of the membrane may include a more substantial degreeof texture (e.g., higher ridges and deeper grooves) to permit ingrowthof muscle tissue to the implant surface. In other examples, designs canbe provided on the exterior surface of the implant to assist inplacement of the implant. For example, guidelines for orientation of theimplant could be molded to the implant surface.

In other preferred and non-limiting embodiments or aspects, an implant12, 112, 210 formed from an elastomeric membrane or shell is filled witha cohesive gel 212. A cohesive gel 212 material refers to asubstantially form-stable material, which maintains its shape whencured. In contrast, flowable materials, such as saline, are not formstable. The cohesive gel 212 is generally a biocompatible material, suchas silicone, which can be injected or poured into an implant shell ormold in a flowable state and cured to produce a form-stable structure.

In some preferred and non-limiting embodiments or aspects, the cohesivegel 212 is enclosed within an elastomeric shell formed from a pluralityof silicone layers. The elastomeric membrane or shell can be undercontraction such that the elastomeric shell exerts a contracting forceon inner portions of the implant, including the cohesive gel. Forexample, outer layers of the shell can be cured to enclose a smallervolume than the volume enclosed by the finished implant. In that case,outer layers of the shell exert a contraction force on inner layers ofthe shell and on the cured cohesive gel material. The contraction forceof the outer layers is balanced against outwardly directed forces of theinner layers and/or cohesive gel. The balance of contracting andoutwardly extending forces contributes to mechanical properties and feelof the implant. For example, inner layers of the membrane and/or thecohesive gel material may press against the outer layers, therebyproviding a level of resiliency and softness, which gives the implant amore natural feel. Previously, manufactures attempted to improve thesoftness and feel of implants by making the shell as thin as possible sothat the feel of the cohesive gel portion of the implant would be morenoticeable than the feel of the shell. In order to make the shell asthin as possible, tougher silicone materials were used for the shell.However, conventional implants formed from thin, tough silicone shellsare susceptible to rippling. In the presently disclosed implant, themembrane is contracted against the cohesive gel, which reducesoccurrence of rippling. In addition, the balance of forces producedbetween the cohesive gel and contracting shell means that a thickershell can be used while still obtaining desirable softness and naturalfeel. Use of a thicker membrane or shell further reduces effects ofrippling.

Exemplary Implant

With reference to FIG. 1, a cross-sectional view of an implant 12 placedwithin the left female human breast is illustrated. The implant 12,according to a preferred and non-limiting embodiment, is in asub-muscular anatomical position under a pectoralis chest muscle 5.Alternatively, the implant 12 can be positioned sub-muscularly or insub-glandular placement. There are variations on these placements, butthese two categories of placement are the most common practice. Thesectional view of FIG. 1 provides basic anatomical landmarks forclarity. The implant 12 is posteriorly positioned against the chest walltissues and underlying ribs 6. Anteriorly, the implant 12 may bepositioned under the chest muscle tissue 5 with the greatest muscularcoverage enveloping the superior anterior aspects of the implant 12.Anterior to the muscle tissues 5 are an intact subcutaneous fat 4 andmammary glands 2. A nipple 3 is the most anterior structure to theimplant 12. As shown in FIG. 1, the implant 12 can be oriented such thata plug 23 that seals the inner cavity of the implant is positionedadjacent to the nipple 3. In other examples, as shown in FIG. 2, theimplant can be positioned with the plug adjacent to the chest wall andunderlying ribs 6.

Elastomeric Membrane

With reference to FIGS. 1-4, according to a non-limiting aspect orembodiment, the implant 12 generally includes an elastomeric membrane,also referred to as a shell, formed from multiple laminated elastomericlayers. In some preferred and non-limiting aspects and examples, themembrane or shell is between about 0.75 mm to 5.0 mm thick, preferablybetween about 1.0 mm and 3.0 mm thick, and more preferably, aboutbetween 1.8 mm and 2.5 mm thick. However, shells having a thickness ofgreater than 5.0 mm may be used for particular applications. In someexamples, the thickness of the membrane can vary around thecircumference of the implant 12. For example, portions of the membraneintended to be positioned near an opening 24 and/or plug 23 may be madethicker than other portions of the membrane. In other examples, portionsof the membrane intended to be positioned near harder anatomicalstructures may be made to be thicker to reduce the possibility ofleakage and/or to improve implant safety.

Generally, the membrane includes at least several high-performancesilicone elastomer layers for enhanced shell integrity. Variableelastomers are utilized to provide a membrane with self-sealingproperties. Although the membrane may include numerous layers, thelayers may be generally classified in two or more zones or regionshaving similar material properties and/or degrees of contraction,namely, an outer zone 18 and an expanded or middle zone 19. In the caseof a two-zone implant 12, only the outer zone 18 and the expanded ormiddle zone 19 are provided. As shown in FIGS. 1, 2, and 4, a three-zoneimplant 12 can include the outer zone 18, the expanded or middle zone19, and an inner zone 20. A two-zone implant 12 is shown in FIG. 3.

In some non-limiting embodiments or aspects, the multiple layers of theelastomeric membrane are classified into the zones based on the volumeenclosed by the respective layers at the time of curing. For example, asdiscussed in greater detail herein, the volume enclosed by the layers ofthe outer zone 18 at the time of curing may be smaller than the volumeenclosed by the layers of the expanded or middle zone 19 at the time ofcuring the middle zone 19 layers, thereby causing the layers of theouter zone 18 to exert a contracting force against the layers of themiddle zone 19. For example, a volume enclosed by the outer zone 18 atthe time of curing may be expanded by between about 10% and about 500%or more before forming the expanded or middle zone 19. In someembodiments, the degree of expansion of the outer zone 18 is selected sothat the completed implant 12 naturally returns to a size which isslightly larger than the size of the outer zone 18 when originallyformed. For example, the completed membrane 214 may naturally conform toenclose an interior volume which is between about 10% and about 40%larger than the volume enclosed by the outer zone 18 at the time offorming the outer zone 18.

In order to impart such a contracting force, at least some of the layersof the outer zone 18 must be durable, essentially impermeable, shouldexhibit stable memory characteristics, and still remain very elastic.For example, the outer zone 18 layers can have a Shore hardness of aboutShore A-10 to A-40, and preferably about Shore A-20 to Shore A-30. Insome examples, layers of the respective zones 18, 20 can be formed atdifferent enclosed volumes. For example, the cured outer zone 18 couldbe expanded incrementally and, during each expansion, a few layers ofthe middle zone 19 could be formed. In this way, the layers of theexpanded or middle zone 19 may be subjected to varying contractingforces based, in part, on the volume enclosed by each respective middlezone 19 layer when formed and/or cured. However, in any case, it isdesirable that in the completed implant 12, expansion and contractingforces provided by the membrane layers are balanced resulting in astable implant. The balance of expansion and contracting forces give thecompleted implant shell desirable properties including, for example,rebound and natural feel.

In some preferred and non-limiting embodiments or aspects, an exteriorsurface of an outermost layer of the outer zone 18 includes one or moretextured portions. For example, textured portions can include a patternof ridges and protrusions for improving implant adhesion. In someembodiments or aspects, the pattern can resemble granulated orcrystalline structures on the implant surface. In other preferred andnon-limiting embodiments or aspects, an exterior surface of an outermostlayer of the outer zone 18 includes a cross-hatch design pattern formedfrom interconnecting lines or waves extending across at least a portionof the implant surface. In other embodiments or aspects, the texturedpattern can include a plurality of protrusions extending from theexterior surface 18 a of the implant 12. For example, such protrusionscan be evenly spaced or positioned across a portion of the exteriorsurface.

Photographic images showing exemplary textured portions of an implant 12are shown in FIGS. 5A-5C. For example, a portion of an implant 12including a textured portion 12 b having a molded granulated orcrystalline structure is shown in FIGS. 5A and 5B. An implant 12 havinga textured portion 12 b having a molded granulated or crystallinestructure and surrounded by a flat portion or surface 12 c is shown inFIG. 5C.

With reference again to FIGS. 1-4, in some preferred and non-limitingembodiments or aspects, the expanded or middle zone 19 includes multiplelayers of softer elastomeric material applied and/or laminated to theouter zone 18 layers. The layers of the middle zone 19 can be formed byblending silicone materials with different hardness to obtain desiredproperties. Desirably, the change in composition of the layers occursgradually so that a transition between adjacent layers is not tooabrupt. Adjacent layers with similar properties adhere together betterthan layers with different properties. For example, layers of theexpanded or middle zone 19 near the outer and inner zones 18, 20 may beformed to have a similar hardness to the outer and inner zones 18, 20.Moving toward the middle of the middle zone 19, the layers can be madeto be gradually softer by increasing the portion of soft siliconematerial in the silicone blend. The total thickness of the middle zone19 may be greater than the outer zone 18. Some or all of the middle zone19 layers may have a tacky, but cured state, which remains soft andelastic. For example, soft, tacky layers of the expanded or middle zone19 can have a durometer of about Shore 00-10 to Shore 00-40. Suchpliable characteristics allow these layers to be put in a state ofcompression. Specifically, as discussed in detail herein, duringformation of the elastomeric membrane, the cured outer zone 18 isexpanded to allow for the larger volumetric form to be established. Oncethe middle zone 19 is cured over the expanded outer zone 18, the outerzone 18 and the middle zone 19 are retracted to a volume and shape thatmore closely resembles its original cured shape. However, the curedouter zone 18 generally is not retracted all the way to its originalstate. Nevertheless, the outer zone 18 still provides substantialcontraction on the softer middle zone 19 by causing the middle zone 19layers to conform to a lesser volume.

In some preferred and non-limiting embodiments or aspects, the outerzone 18 and/or the expanded or middle zone 19 can include a combinationof soft and hard layers. For example, soft and hard layers can belaminated one on top of the other in alternating fashion, therebyproviding a zone 19, 20 including both soft and hard properties.

For an elastomeric membrane having only two zones, as shown, forexample, in FIG. 3, at least an innermost layer 19 a of the middle zone19 should be harder than the other layers of the middle zone 19, therebyenclosing and providing a contracting force for the soft tacky layers ofthe middle zone 19. However, unlike for a three-zone membrane in whichthe inner zone 20 is cured after the membrane 12 is retracted, theinnermost layer 19 a of the middle zone 19 is formed while the membraneis in an expanded state. For example, the harder innermost layer 19 amay be formed on the inner surface of the middle zone 19 just before themembrane is retracted. The innermost layer 19 a may have a compositionsimilar to the harder and more rigid layers of the outer zone 18.

In some preferred and non-limiting embodiments or aspects, the membranecan define an opening 24 for permitting access to the interior of theimplant 12 during formation and filling. For example, a plug 23 can beinserted and cured in the opening 24 to seal the interior volume of theimplant. In some examples, the plug 23 functions as a self-sealinginjection port that can be utilized to pre-fill the implant 12 enclosedby the membrane to a desired volume prior to implantation. This plug 23may take a variety of forms and configurations, such as a one-way valve,a flapper valve, an elastic valve, and the like. Further, the plug 23may include one or more apertures or conduits through which to insertspecified fluids into various areas of the implant 12.

In other preferred and non-limiting embodiments or aspects, the plug 23is formed by folding a small portion of the elastomeric layers of themembrane over the opening 24 to seal the opening 24. For example, asshown in FIGS. 16-18, the formed membrane can include a neck portionextending from the opening 24 which must be removed to form thecompleted implant. The neck portion is often cut off after theelastomeric membrane is cured. In some examples, portions of the neckportion can be folded into the opening 24 to form the plug 23 ratherthan being cut off from the implant. In other embodiments or aspects,the plug 23 is a flat patch or piece of elastomeric material which ismounted to the implant 12 over the opening 24 using, for example,adhesive or flowable elastomeric material. The flowable elastomericmaterial can be cured to secure the patch to the elastomeric membrane.In other embodiments or aspects, the plug 23 can be formed by pouring asmall amount of flowable silicone in the opening 24. The flowablematerial can be cured to form a suitable seal for the implant.

After the layers of the membrane are cured, in some preferred andnon-limiting embodiments or aspects, the chamber or interior volume ofthe implant 12 can be filled with biocompatible fillers, such as salineor saline with biocompatible thickening agents, so that in the event ofleaking, the saline is naturally absorbed. Thickening agents can bedesigned to provide additional sealing ability from within the implant.Methylcellulose has a high molecular mass and can be added to the salineto give it gel-like properties. Aqueous carboxy-methylcellulose hasproven biocompatibility and is utilized in some cosmetic filling agents.Polyethylene glycol (PEG) and saline would also be a suitablecombination with thickening characteristics. The high molecular mass ofPEG and other similar thickening agents will reduce the risk of leakagefrom the membrane. Previously, membranes of breast implants weregenerally made as thin as possible to achieve a softer feel. However,thinner membranes impose greater risks with respect to puncture,capsular contraction, and gel or fluid bleeds. The membranes describedherein are generally thicker than currently available membranesresulting in a safer design. For example, the membrane is preferablyabout 1.8 mm to 3.0 mm thick, and can be as thick as 5.0 mm. Thecontraction properties of the present implant 12 are selected to providethe desirable natural, soft feel even when a thicker membrane is used.

Exemplary Three-Zone Implant

With reference to FIG. 4, an implant 12 comprising a three-zone shell isillustrated. An implant 12 having a membrane formed in a three-zoneconfiguration facilitates the self-sealing capability of the implant 12.The implant 12 is generally similar in size and shape to the otherexemplary implants described herein. For example, the implant 12generally includes a continuous or substantially continuous elastomericmembrane that has a total thickness of about 0.75 mm to 5.0 mm,preferably about 1.0 mm to 3.0 mm, and more preferably about 1.8 mm to2.5 mm thick. The membrane encloses a volume or chamber of about 80 ccto 800 cc. The membrane includes the outer zone 18 formed from a hardersilicone material of about Shore A-10 to Shore A-40, and preferably fromabout Shore A-20 to Shore A-30. The elastomeric layers of the outer zone18 enclose and apply substantial compression to soft, tacky, but curedlayers of the middle zone 19. As discussed in connection with otherexemplary implants, the layers of the middle zone can have a durometerof about Shore 00-10 to Shore 00-40.

The membrane further comprises an inner zone 20 formed from one or moreelastomeric layers that are strong and highly resistant to permeability.The layers of the inner zone 20 remain elastomeric and have significantability to stretch and return to their original shape. These inner zone20 layers are cured and set to a desired volume and shape, whichencapsulates the interior volume or chamber of the implant 12. Asdescribed herein, the layers of the inner zone 20 are formed when themembrane is in a retracted state. Accordingly, the layers of the innerzone 20 exert a contracting force to the layers of the middle zone 20contributing to the substantial compression on the middle zone 20.Accordingly, the inner zone 20 contributes to the desirable propertiesof the implant 12 by enhancing compression on the middle zone 19.

In a three-zone implant, the middle zone 19 includes multiple layers ofsofter elastomeric material to envelop the inner zone 18 layers in asignificantly expanded state. The middle zone 19 may be thicker than theinner zone 18 or the outer zone 20. During formation of the membrane,the inner zone 18 is expanded to allow for the larger volumetric form tobe established. Once the middle zone 19 is cured, the inner zone 18 andthe middle zone 19 are retracted to a volume and shape representative ofthe inner zone 18 in its original cured shape. Thus, the softer middlezone 19 is in significant contraction as it is forced to conform to alesser volume. The outer zone 20 layers are then formed to envelope themiddle zone 19 layers. The outer zone 20 has similar or identicalproperties to the inner zone 18 layers, being elastomeric, yet strongand resistant.

The resultant membrane includes a middle zone 19 that is thicker andformed from softer elastomeric membrane, under contraction. The middlezone 19 is sandwiched between the inner zone 18 and the outer zone 20 ofstronger and more stable elastomeric compounds. In some embodiments oraspects, the membrane may be different thicknesses at different areas ofthe implant 12. Further, as discussed above, the harness of the layersof the middle zone 19 can vary gradually such that adjacent layers ofthe membrane have similar mechanical properties.

The three-zone configuration can facilitate the self-sealing capabilityof the membrane. However, the design and configuration of the membraneis not limited to the three-zone configuration. Other arrangements ofelastomeric layers may also be employed to provide the self-sealingability of the membrane. Furthermore, as will be appreciated by onehaving ordinary skill in the art, manipulation of these zone layers andtheir configuration will produce further advantages of this invention.For example, multiple layers under contraction will increase theintegrity and self-sealing potential of the membrane. Thickness of thelayers under contraction also relates directly to integrity of themembrane. Therefore, a balance between the optimal number of layers andlayer thickness should be established for particular applications.

In some preferred and non-limiting embodiments or aspects, the implant12 formed from a three-zone membrane can be punctured with a non-coringneedle to access one or more chambers enclosed by the membrane.Non-coring needles are used to puncture the membrane without removingany of the silicone material forming the membrane layers. The geometryof a non-coring needle spreads and expands the silicon at the entrysite. Upon retraction of the needle from the membrane, the siliconeself-seals at the penetration site. The silicone must be undercontractive forces to self-seal. This contraction is achieved byretaining the silicone membrane under mechanical compression from otherelastomeric layers.

The self-sealing properties of the membrane produces an implant shellexhibiting properties different from existing implants. The compressionof the middle zone 19 changes how the inflation forces are manifested interms of the general feel of the implant 12. More specifically, theimplant 12 can be varied in design to produce a more natural feel withless of an inflated or balloon characteristic. Furthermore, theproperties of the membrane introduce a favorable variable that can beincorporated in various single or multiple chamber designs. For example,it is possible to alter the characteristics of the membrane to produce asaline-filled implant with more silicon-like characteristics.

Method of Forming the Implant

Having generally discussed the structure of different embodiments of anelastomeric membrane and implant, methods of manufacture of suchimplants will now be described in detail. As will be appreciated by oneof ordinary skill in the art, the manufacturing possibilities for suchimplants are extensive with respect to methods and materials.

Reverse Casting Method

In some preferred and non-limiting embodiments or aspects, the membraneis formed in a mold in reverse order (e.g., a reverse casting method)from an exterior layer to an innermost layer. The methods disclosedherein also include varying a volume enclosed by the respective layers,thereby imparting a substantial contracting force, particularly to themiddle layer 19 of the implant 12.

With reference to FIGS. 6-11, a method of forming the implant 12 bycasting into a mold is illustrated. Various methods of casting may beemployed from simple manual techniques to mechanical spin casting. Thelayers of the respective zones 18, 19, 20 are cast and cured in thereverse order, starting with the layers of the outer zone 18. As shownin FIG. 6, a mold 17 is utilized to produce the viscoelastic layers ofthe outer zone 18, which are, desirably, very durable, essentiallyimpermeable, exhibit stable memory characteristics, and still remainvery elastic. In some preferred and non-limiting embodiments or aspects,the mold 17 is formed from a clear material to permit visual inspectionduring the casting process. The mold 17 may be a flexible structure thatcan be expanded and contracted to form layers and/or zones havingdifferent enclosed volumes. For example, the mold 17 can be formed fromvarious flexible and stretchable plastics. In other embodiments oraspects, the mold 17 can be formed from a rigid, non-expandablematerial, such as glass, having a constant volume and used solely forforming the layers of the outer zone 18. In that case, other zones(e.g., the middle zone 19 and/or the inner zone 20) can be formed oncethe cured layers of the outer zone 18 are removed from the mold 17. Forexample, as discussed herein, the cured outer zone 18 can be insertedinto an expandable bladder 17 a during formation of the middle and/orinner zones 19, 20. In other examples, the cured outer zone 18 may besufficiently rigid that the middle and/or inner zones 19, 20 can beformed in the cured outer zone 18 without using a mold or bladder tosupport the cured outer zone 18.

In some examples, the mold 17 can be disposable and configured to beused one time. For example, molds formed from plastics can beinexpensive to manufacture and can be discarded after a single use.Advantageously, implants formed from a disposable mold can be highlycustomized for particular uses. For example, implant volume and shapecan be customized for particular patients. In addition, texturing on theinner surface of the mold can be specifically adapted for particularuses.

As shown in FIG. 6, a flowable material, such as liquid silicone, isintroduced to an interior of the mold 17. The flowable material can bedispersed across the inner surface of the mold 17 by spinning and/orinverting the mold 17 until the entire surface is covered. The flowablematerial desirably flows into the texturing, ridges, and channels on theinner surface of the mold 12, such that the exterior surface of theouter zone 18 conforms to the texturing of the inner surface of the mold17. Once the flowable material is evenly dispersed, it can be allowed tostabilize and cure. In some examples, the flowable material cures atroom temperature. In other examples, the mold 17 and flowable materialcontained therein can be heated to cure the flowable material, therebyforming an elastomeric layer. Additional layers of the outer zone 18 canbe laminated to the inner surface of the outermost layer 18a, therebyforming a thicker outer zone 18. The outer zone 18 can be complete oncethe collected layers reach a desired thickness. The purpose of thisinitial stage is to produce a complete form of the viscoelastic layersof the outer zone 18 as seen in FIG. 6. An illustration of a cured outerzone 18 removed from the mold 17 is shown in FIG. 7.

As shown in FIG. 8, an apparatus 33, such as a vacuum evacuationchamber, is used to expand and retract the cured outer zone 18 and/ormold 17 to cast the remaining layers. The outer body of the apparatus 33is rigid with an evacuation valve 34 and an internal bladder 17 a. Thepurpose of this apparatus 33 is to expand and retract the outer zone 18layers and/or mold 17 through the remainder of the laminating process.The bladder 17 a has a base shape reflective of the final form of thepreferred and non-limiting embodiment of the implant illustrated, forexample, in FIGS. 1-4. The bladder 17 a has elastic properties andstrong memory of form. In some examples, the bladder 17 a may includeperforations to allow communication between the mold cavity andevacuation chamber 35 created by the outer body of the apparatus 33.

With continued reference to FIG. 8, the previously formed outer zone 18viscoelastic layers are positioned within the bladder 17 a. In someexamples, the outer zone 18 layers can remain in the mold 17, and boththe zone 18 and mold 17 can be inserted in the bladder 17 a. In otherexamples, the outer zone 18 layers can be removed from the mold 17 andinserted in the bladder 17 a. The cured outer zone 18 can be inserteddirectly in the evacuation chamber 35 without a supporting mold 17 orbladder 17 a. Once inserted in the chamber 35, the bladder 17 a can beretracted to conform to the shape of the cured outer zone 18. A slightvacuum pressure may be required to hold the outer zone 18 layers and/ormold 17 in place. The bladder 17 a and outer zone 18 layers are sealedaround a collar of the apparatus 33 body. The vacuum pressure ismaintained by utilizing an evacuating valve 34. In certain embodiments,the contact surface between the bladder 17 c and the viscoelastic layersof the outer zone 18 may require lubrication to equalize and marry theconforming shapes. Once positioned and retained, the apparatus 33 isconfigured to expand the bladder 17 a along with the outer zone 18viscoelastic layers to a desired size and shape.

As shown in FIG. 9, the complex of the bladder 17 a and the previouslyformed outer zone 18 layers are expanded and retained in an expandedform by closing the evacuation valve 34 to seal the evacuation chamber35. For example, if the layers of the outer zone 18 have a cureddiameter of 7 cm and an enclosed volume of 180 cm³, in the expandedform, the outer zone 18 can have a diameter of about 15 cm and anenclosed volume of about 1770 cm³. Once expanded the desired amount, theexpanded mold cavity is ready to laminate the middle zone 19 layers. Insome examples, as discussed herein, one or more of the middle zone 19layers are required to attain a tacky, but cured state, which remainssoft and elastic. In particular, these middle zone 19 layers desirablyhave pliable characteristics that allow the layers to be placed in astate of compression. The middle zone 19 layers are cast in one or morelayers by manual or mechanical processes, similar to the previously castouter zone 18 layers.

In some preferred and non-limiting embodiments or aspects, the implant12 can be formed as a two-zone implant including only elastomeric layersof the outer zone 18 and the middle zone 19. In that case, at least theinnermost layer 19 a of the middle zone 19 is a harder layer similar tothe layers of the outer zone 18. In order to deposit the hard innermostlayer 19 a of the middle zone 19, after forming the soft and tackylayers of the middle zone 19 in the manner described above, theinnermost layer 19 a is formed by introducing a harder elastomericmaterial to the interior cavity of the mold 17, dispersing theelastomeric material over the surface of the membrane, and curing thematerial to form the hard innermost layer 19 a.

After casting of the middle zone 19 layers is complete, the layers aresubjected to compression by opening the evacuation valve 34 to place thecured outer zone 18 and middle zone 19 in a retracted state. The processof retraction may be done in a cured or partially cured state to allowmanipulation of desired characteristics of the membrane complex. Thisallows the bladder 17 a to return to its original memory shape with thelaminated outer zone 18 layers and middle zone 19 layers. It is notedthat although the bladder 17 a may return to its original shape, thelayers of the outer zone 18 generally do not retract all the way totheir original cured shape and position but, instead, assume a slightlyexpanded configuration compared to the original cured state. Forexample, for a shell in which the outer zone 18 has a cured diameter ofabout 7 cm and an enclosed volume when cured of about 180 cm³, the finalor retracted diameter of the outer zone 18 can be about 9 cm and have anenclosed volume of about 382 cm³. Accordingly, the textured exteriorsurface of the outer zone 18, formed from contact between the outer zone18 and the inner surface of the mold 17, is not an identicalrepresentation of the texturing and/or ridges and channels on the innersurface of the mold 17. Instead, the texturing on the exterior surfaceof the implant 12 assumes a slightly expanded configuration. Thetexturing on the inner surface of the mold 17 can be selected with thedegree of expansion of the formed implant 12 in mind.

The formed elastomeric membrane can be removed from the mold 17 andpre-stressed prior to filling to modify the resiliency and elasticity ofthe implant. In some embodiments or aspects, pre-stressing includesstretching the membrane by expanding the volume enclosed by the membraneby a substantial amount. Some implants 12 formed by the processesdescribed herein can be expanded by up to 3000% without rupture (e.g., a500 cc implant was expanded to 15 L). In other examples, pre-stressingthe membrane can include stretching portions of the membrane to increaseflexibility of selected portions of the implant. Further, in someinstances, pre-stressing can include performing multiple inflationsand/or adjusting a duration of each inflation or ambient temperatureduring inflation of the membrane. In other examples, the amount ofstretching or percentage of inflation can be adjusted. In someembodiments or aspects, especially for thicker elastomeric membranes,the membrane may be warmed or heated prior to stretching or stressing.In one example, external pressure (e.g., squeezing) can be applied toportions of the membrane as it is being inflated to impart variablepre-stressing. For example, if the two poles of the implant 12 arepushed with a force towards one another, the equatorial portion of theimplant 12 will expand more causing that portion of the membrane to besofter and more pliable after the pre-stressing process is complete.

Following pre-stressing, in some preferred and non-limiting aspects orembodiments, the interior volume or void of the membrane is cleaned byappropriate measures. After cleaning, the membrane can be enclosed bytrimming surplus membrane formed along the apparatus 33 collar andinverting a flange remaining around the hole or opening 24 of themembrane in an inward direction toward the middle of the posterioraspect of the implant 12 to form the plug 23. The plug 23 is then curedto seal the implant 12, thereby forming a completed two-zone implant.Exemplary completed two-zone implants are illustrated, for example, inFIGS. 3 and 11.

In some preferred and non-limiting embodiments or aspects, the plug 23is formed from viscoelastic material similar to the middle zone 19. Theplug 23 functions as a self-sealing injection port that can be utilizedto pre-fill the interior volume or chamber 25 of the implant to adesired volume prior to implantation. Biocompatible thickening agentscan also be pre-filled prior to sealing the implant. The implant 12 isfilled or partially filled with a fluid, such as saline, prior toimplantation to the patient.

With reference to FIGS. 12-15, a process for forming a three-zoneimplant 12 is illustrated. The process generally resembles the processfor making the two-zone implant described in connection with FIGS. 6-11.In particular, as shown in FIG. 12, the elastomeric material isintroduced to the mold 17 and cured to form the outer zone 18. Texturingcan be transferred from the inner surface of the mold 17 to the exteriorsurface of the implant in the manner discussed herein. In someembodiments or aspects, after curing, the outer zone 18 is removed fromthe mold 17 and placed in the bladder 17 a. In other examples, the mold17 and cured outer zone 18 are inserted in the bladder 17 a together. Asshown in FIG. 13, the outer zone 18 and/or mold 17 are expanded andretained in an expanded form by closing the evacuation valve 34 to sealthe evacuation chamber 35. As in previously described examples, theexpanded mold cavity is ready to laminate the middle zone 19 layers. Insome examples, one or more of the middle zone 19 layers are required toattain a tacky, but cured state, which remains soft and elastic. Thesemiddle zone 19 layers may have pliable characteristics that allow thelayers to be placed in a state of compression. The middle zone 19 layersare cast in one or more layers by manual or mechanical processes,similar to the previously cast outer zone 18 layers.

After the middle zone 19 is cured, the shell, including the outer zone18 layers and the middle zone 19 layers, is retracted, in the mannerdescribed above. Once the zones 18, 19 are retracted, as shown in FIG.14, the apparatus is configured for a final molding state. Specifically,the outer zone 18 and middle zone 19 are retracted to a shaperepresentative of the final form of the implant 12. Adequate vacuumpressure remains in the evacuation chamber 35 to stabilize the form formolding. Once the membrane is stabilized in a desired form, one or moreviscoelastic layers of the inner zone 20 are cast in a manner similar tothe previously cast layers. For example, flowable viscoelastic materialfor forming layers of the inner zone 20 can be introduced to theinterior surface of the membrane or shell either manually (e.g., bypouring flowable elastomeric material into the mold) or using amechanical or automated device for introducing such flowable material.In some preferred and non-limiting embodiments or aspects, the innerzone 20 layers are very durable, essentially impermeable, exhibit stablememory characteristics, and still remain very elastic.

In some preferred and non-limiting embodiments or aspects, the membranecan be sealed by a plug 23 in the manner described above in connectionwith the two-zone elastomeric membrane. In other examples, the membranecan be sealed by one or more layers of the inner zone 18, as shown inFIG. 15. For example, the layers of the outer zone 18 and the middlezone 19 may define an opening 24 for permitting casting of additionallayers in the interior of the void space or chamber. The innermost layerof the inner zone 20 can be formed as a continuous layer extending intothe opening 24 to seal the membrane. Once the layers of the inner zone20 are in place, the inner zone 20 can be cured to produce the completedimplant 12. Once the inner zone 20 layers are cured, the three-zonemembrane is complete and ready for removal. The vacuum is released andthe laminated implant shell is pulled through the collar of theapparatus 33 neck.

In some preferred and non-limiting embodiments or aspects, the implant12 may be filled in the mold 17. For example, prior to enclosing theinner zone 20, a biocompatible gel may be introduced to the implant 12cavity or void space. Biocompatible thickening agents can also bepre-filled prior to sealing the implant 12. The implant 12 is filled orpartially filled with a fluid, such as saline, prior to implantation toa patient. Once the fluid is introduced, the cavity can be enclosed inany of the manners described herein. For example, the plug 23 can becured in the opening 24 or a portion of the inner zone 20 can be formedto enclose the opening 24. The filled implant 12 can be removed from themold 17 by breaking the mold 17 in half. In other examples, the mold 17can be a reusable two-piece mold. In that case, the filled implant 12can be removed from the mold 17 by separating the pieces of the mold 17and removing the filled implant 12 therefrom.

In other preferred and non-limiting embodiments or aspects, the mold 17can be formed from a degradable or dissolvable material. In that case,after the layers of the inner zone 20 are cured and/or after thecompleted implant 12 is filled, the mold 17 can be dissolved to releasethe implant 12 therefrom. In some embodiments or aspects, dissolving themold 17 can comprise placing the mold 17 and formed implant 12 into abath of a fluid capable of dissolving the mold 17. For example, the mold17 may be formed from collagen. In that case, the collagen mold 17 canbe dissolved by immersion in a solution of acetic acid or anothersuitable fluid.

In other examples, as discussed in connection with the two-zoneembodiments, the formed implant 12 can be removed from the mold 17before filling. After the implant 12 is removed, it can be filled to adesired amount for a particular patient and/or use. In that case, theunfilled implant can be removed through a small opening of the apertureand without breaking the mold. The mold can then be reused for formingadditional implant devices. Other suitable steps for removing theimplant from the mold, and filling the collapsed implant with abiocompatible gel or liquid, and preparing the formed implant forpatient treatment will be apparent to those of ordinary skill in theart.

Drip Casting Method

In other preferred and non-limiting embodiments or aspects of amanufacturing process, drip casting can be employed to form theelastomeric membrane. Drip casting around a mandrel is a moreconventional method of forming the primary shell of a breast implant.FIGS. 16-27 show different processes for forming viscoelastic membranesaround mandrels.

With reference to FIGS. 16-27, methods of forming an elastomericmembrane by drip casting about a mandrel 117 are discussed herein.Generally, the inner zone 118 layers are formed on the mandrel 117. Themandrel 117 is then wasted, collapsed, or removed from the formedlayers. There are many potential materials that can be utilized to formthe mandrel 117. Gypsum plaster is a good example; however, variousplastics could be employed as well. A plastic mandrel can bemechanically collapsed, softened with solvents, or heated to aid inremoval without damaging the silicone castings. Gelatinous substancesare another option that can provide sufficient stability to expand amembrane and form a mandrel that can be wasted and removed. Agar oragar-agar is one such form of a polysaccharide that can be molded intofirm stable shapes. The possibilities for casting are extensive anddifferent techniques may be employed for various applications of thisinvention.

In a preferred and non-limiting embodiment or aspect of a manufacturingprocess, after the formed membrane is removed from the mandrel 117, anexpansion medium 122 is utilized to expand the formed layers duringlater steps of the casting process. Such a medium 122 is necessary toretain the previously cast membrane in a desired expanded state, as wellas to support a membrane volume in a retracted state. The expansionmedium 122 has many possible choices of materials and techniques ofemployment. Gasses and fluids under pressure are the simplest mediumsthat can be used. Agar and other materials that can be poured and castto a fixed volume and shape can also be utilized. Agar has a low meltingpoint, which allows it to be liquefied for removal or recast asrequired. Beads are another option that can produce fixed volumes ofvariable shapes. The advantages and disadvantages of various expansionmediums will be apparent based on the requirements of the particularstage of manufacture.

A first preferred and non-limiting manufacturing method using dripcasting about a mandrel 117 is shown in FIGS. 16-19. FIG. 16 is asectional view of the drip casting mandrel 117. The mandrel 117 isformed from a material that will be destroyed after the inner zone 118layers are cast. Thus, the mandrel 117 can be described as a waste dripcasting mandrel. The mandrel 117 can be cast in gypsum plaster. Thegypsum plaster is a viable option, as it can be cast very thin and canbe easily removed by mechanical means and/or dissolved with sodiumbicarbonate and water. Multiple elastomeric layers are drip cast ontothe mandrel 117 to form the inner zone 118 of the membrane. The innerzone 118 viscoelastic layers must be very durable, essentiallyimpermeable, exhibit stable memory characteristics, and still remainvery elastic.

In FIG. 17, the mandrel 117 has been wasted and the inner zone 118 shellhas been filled with expansion medium 122 through a filling tube 121 forthe purpose of expanding the shell to a desired volume. The expansionmedium 122 is required to be a stable medium that can be altered involume. The filling tube 121 has three functions. It inflates the innershell 118, allowing the expansion medium 122 to pass through it and fillthe expanded volume. Once the desired form is achieved, the filling tube121 becomes a supporting handle, which creates a drip casting mandrel toapply the middle zone 119 viscoelastic layers. The middle zone 119layers are applied directly on top of the inner zone 118. The middlezone 119 layers have a tacky, but cured state, which remains soft andelastic. Such pliable characteristics allow these layers to be put in astate of compression.

FIG. 18 illustrates the third drip casting state. In this form, aportion of the expansion medium 122 has been removed to return themembrane to a volume and shape representative of the original mandrel117. The filling tube 121 is utilized to create a vacuum retracting theinner zone layers and compressing the middle zone layers 119 to conformthereto. The outer zone 120 layers are drip cast to encase the middle119 and inner zone 118 layers. The three-zone shell is complete when theouter zone 120 layers are cured. These outer zone 120 viscoelasticlayers must be very durable, essentially impermeable, exhibit stablememory characteristics, and still remain very elastic. The layers of theouter zone 120 are essentially the same as, or similar to, the innerzone 118 viscoelastic layers.

FIG. 19 illustrates a non-limiting and preferred embodiment of theimplant 110 formed from a three-zone membrane in its completed state. Toproduce the implant 110, the expansion medium 122 is removed producing avoid shell. The shell is cleaned and surplus membrane, formed along thefilling tube 121, is trimmed away. The flange remaining around the holethat remains in the middle of the posterior aspect of the implant isinverted inward and a plug 123 is cured to seal the implant 112. Theplug 123 is formed from a viscoelastic material, similar to the materialthat forms the middle zone 119. The plug 123 functions as a self-sealinginjection port that can be utilized to pre-fill a main chamber 125 ofthe implant 112 enclosed by the membrane to a desired volume prior toimplantation. This plug 123 may take a variety of forms andconfigurations, such as a one-way valve, a flapper valve, an elasticvalve, and the like. Further, the plug 123 may include one or moreapertures or conduits through which to insert specified fluids intovarious areas of the implant 112. Biocompatible thickening agents canalso be pre-filled prior to sealing the implant 112. The implant 112 isfilled or partially filled with a fluid, such as saline, prior toimplantation to a patient.

In another preferred and non-limiting embodiment or aspect, the mandrel117 is an expandable structure which can be used for forming layers ofthe inner zone 118, expanded or middle zone 119, and, optionally, theouter zone 120. For example, an expandable mandrel 117 may be aninflatable balloon formed from a flexible rubbery material. Desirably,at least an outer surface of the expandable mandrel 117 is not formedfrom silicone to prevent portions of the implant membrane from adheringto the mandrel 117 during curing. A volume of the expandable mandrel 117or balloon can be increased by inflating the mandrel 117 with a fluid(e.g., air or saline solution) to adjust the mandrel volume. Forexample, layers of the inner zone 118 may be formed around the mandrel117 in the manner described hereinabove. After the layers of the innerzone 118 are cured, the mandrel 117 can be expanded by introducing fluidto the interior of the mandrel 117. Once the mandrel 117 is expanded,layers of the expanded or middle zone 119 can be formed around theexpanded inner zone 118 in the manner described hereinabove. After themiddle zone layers 119 are cured, the mandrel 117 can be collapsed byremoving fluid from the interior of the mandrel 117, thereby reducingthe volume of the mandrel 117 to a volume enclosed by the layers of theinner zone 118 at the time of curing. Once the mandrel 117 is collapsed,layers of the outer zone 120 can be formed over the middle zone 120 inthe manner previously described by, for example, pouring liquid siliconeover the layers of the middle zone 119. After the outer zone 120 is inplace, the layers of the outer zone 119 can be cured. Following curingof the outer zone 120, the mandrel 117 can be collapsed or deflated andremoved from mandrel 117 by, for example, sliding the collapsed ordeflated mandrel through the opening of the formed elastomeric membrane.

With reference to FIGS. 20-23, steps for forming another preferred andnon-limiting embodiment of an implant by drip casting are illustrated.FIG. 20 is sectional view of a dual-chamber drip casting mandrel 117used to form the inner zone 118 of the implant 112. The mandrel 117 isformed to a desired shape out of a material that will be destroyed afterthe inner zone 118 layers are cast to its form. The mandrel 117 can bedescribed as a waste drip casting mandrel. The mandrel 117 can be castin gypsum plaster. The gypsum plaster can be cast very thin and can beeasily removed by mechanical means and/or dissolved with sodiumbicarbonate and water. Multiple elastomeric layers are formed on themandrel 117 to form the inner zone 118. The inner zone 118 viscoelasticlayers must be very durable, essentially impermeable, exhibit stablememory characteristics, and still remain very elastic.

In FIG. 21, the dual chamber mandrel 117 has been wasted and bothchambers of the inner zone 118 shell have been filled with the expansionmedium 122 for the purpose of expanding the shell and retaining it to adesired volume. The filling tube 121 has three functions. It inflatesthe inner shell allowing the expansion medium 122 to fill the expandedvolume. Once the desired form is achieved, the filling tube 121 becomesa supporting handle creating a drip casting mandrel to apply the middlezone 119 viscoelastic layers. The middle zone 119 layers are formeddirectly on the inner zone 118 and cured. As in previously describedembodiments or aspects, the expanded or middle zone 119 layers attain atacky, but cured state, which remains soft and elastic. Further, in someembodiments or aspects, pliable layers of the expanded or middle zone119 are capable of being put in a compression state.

FIG. 22 illustrates the third drip casting state. In this form, aportion of the expansion medium 122 is removed to return the membrane toa volume and shape representative of the original mandrel 117. Thefilling tube 121 is utilized to create a vacuum retracting the innerzone 118 layers and compressing the middle zone 119 layers to conformthereto. The outer zone layers 120 are drip cast to encase the middle119 and inner zone 118 layers. The three-zone membrane is completed whenthe outer zone 120 layers are cured. These outer zone 120 viscoelasticlayers must be very durable, essentially impermeable, exhibit stablememory characteristics and still remain very elastic. Thus, they areessentially the same as or similar to the inner zone 118 viscoelasticlayers.

FIG. 23 illustrates a preferred and non-limiting embodiment of theimplant 112 in a completed state, formed from the elastomeric membranedepicted in FIGS. 21 and 22. To form the implant 112, the expansionmedium 122 is removed producing a void shell. The shell is cleaned byappropriate measures. After cleaning, a smaller inner chamber 127 of themembrane is folded into an outer chamber 126, thereby forming an implantin which the outer chamber 126 encloses the inner chamber 127. Thus, theinner chamber 127 membrane is inverted in its final position. Further, aportion of the continuous membrane formed along the filling tube 121becomes the termination of the membrane. As this portion of the membraneexits the posterior aspect the implant 112, surplus is trimmed away.Next, a plug 123 is inserted and cured to seal the implant 112. The plug123 is formed from viscoelastic material similar to the middle zone 119.In some embodiments, the plug 123 functions as a self-sealing injectionport that can be utilized to pre-fill the outer chamber 126 and innerchamber 127 of the implant to a desired volume prior to implantation.Biocompatible thickening agents can also be pre-filled prior to sealingthe implant. In this final configuration, the implant 112 has acontinuous viscoelastic membrane forming two self-sealing independentchambers. The implant 112 is filled or partially filled with a fluid,such as saline, prior to implantation to a patient.

With reference to FIGS. 24-27, a method of manufacture of anotherpreferred and non-limiting embodiment or aspect of an adjustable implant113 is illustrated. FIG. 24 is sectional view of a three-chamber dripcasting mandrel 117 used for the initial forming of implant 113,according to a preferred and non-limiting embodiment or aspect of theinvention. The mandrel 117 is formed to a desired shape out of amaterial that will be destroyed after the inner zone 118 layers are castto its form. The mandrel 117 can be described as a waste drip castingmandrel 117. In some embodiments, the mandrel 117 can be cast in gypsumplaster. The gypsum plaster can be cast very thin and can be easilyremoved by mechanical means and/or dissolved with sodium bicarbonate andwater. Multiple elastomeric layers are drip cast to the mandrel 117 toform the inner zone 118. The inner zone 118 viscoelastic layers must bevery durable, essentially impermeable, exhibit stable memorycharacteristics, and still remain very elastic.

In FIG. 25, the three-chamber mandrel 117 is wasted and the main chamberof the inner zone 118 shell is filled with the expansion medium 122 forthe purpose of expanding the shell and retaining it to a desired volume.The filling tube 121 requires a retaining clip 124 to seal the neck tothe outer chamber 126 and also pull the two smaller chambers(collectively inner chamber 127) away from the outer chamber 126. Thefilling tube 121 has three functions. It inflates the inner zone 118shell of the outer chamber 126 allowing the expansion medium 122 to passthrough it and fill the expanded volume. Once the desired form isachieved, the filling tube 121 becomes a supporting handle creating adrip casting mandrel. The middle zone 119 viscoelastic layers areapplied directly to portions of the inner zone 118. In a preferred andnon-limiting embodiment, the middle zone 119 viscoelastic layer is onlydrip cast on the outer chamber 126. The middle zone 119 layers arerequired to attain a tacky, but cured state which remains soft andelastic. These pliable characteristics mean that the middle zone 119layers can be placed in a state of compression.

FIG. 26 illustrates the third drip casting state. In this form, aportion of the expansion medium 122 is removed to return the outerchamber 126 to a volume and shape representative of the original mandrel117. The expansion medium 122 is also added to the inner chambers 127 tofill them to a volume and shape representative of the original mandrel117. The filling tube 121 is utilized to create a vacuum pressure,thereby retracting the entire structure and compressing the middle zone119 layers to conform thereto. The outer zone 120 layers are drip castto encase the middle zone 119 and inner zone 118 layers. Thethree-chamber shell is complete when the outer zone 120 layers arecured. These outer zone 120 viscoelastic layers must be very durable,essentially impermeable, exhibit stable memory characteristics, andstill remain very elastic. They are essentially the same as or similarto the inner zone 118 viscoelastic layers. The final three-chamber shellconsists of an outer chamber 126 shell which has the three layerself-sealing properties. The two smaller chambers (collectively innerchambers 127) only include inner zone 118 and outer zone 120 layers.

FIG. 27 illustrates another preferred and non-limiting embodiment oraspect of an implant 113 formed from the membrane layers of FIGS. 25 and26, in its completed state. In order to produce the completed implant113, expansion medium 122 is removed producing a void shell. The shellis cleaned through appropriate measures. The two smaller chambers(collectively inner chambers 127) are folded into the outer chamber 126.Thus, the inner chamber 127 membrane has an inverted outer aspect andnon-inverted inner aspect in its final position. A portion of thecontinuous membrane along the filling tube 121 forms the ends of themembrane. A port for accessing the outer chamber 126 of the membrane ispositioned at the ends of the membrane. Surplus material is trimmed fromthis portion of the membrane. A plug 123 is inserted and cured to sealthe implant 113 in the port. As in previous embodiments, the plug 123can be formed from viscoelastic material similar to the middle zone 119.The plug 123 functions as a self-sealing injection port that can beutilized to pre-fill the outer chamber 126 and inner chamber 127 of theimplant 113 to a desired volume prior to implantation. Biocompatiblethickening agents can also be pre-filled prior to sealing the implant.It is noted that the inner chamber 127 may be perforated to allow fluidcommunication of all chambers. In this embodiment, inner structures ofthe implant 113, namely the inner chamber 127, provide bafflingcharacteristics to calm fluid motion of the liquid utilized to fill thechambers. The implant 113 is filled or partially filled with a fluid,such as saline, prior to implantation to a patient.

With reference to FIGS. 28-30, steps for forming an adjustable implant114 according to another preferred and non-limiting embodiment or aspectof the invention are illustrated. FIG. 28 depicts a completed shellformed by drip casting around a mandrel, including inner zone layers118, middle layers 119, and outer zone layers 120. In FIG. 28, theexpansion medium 122 is removed producing a void shell. The shell iscleaned after the expansion medium 122 is removed. The shell is inflatedenough to maintain its shape and a temporary plug 130 is positioned nearan opening of the shell. Viscoelastic tendrils 129 are formed and curedon one of the chambers of the shell.

FIG. 29 depicts the next formation stage, where the entire membrane isinverted upon itself, such that tendrils 129 extend inward into theinner chamber 127. The final configuration of the implant 114 withtendrils 129 is illustrated in FIG. 30. The smaller inner chamber 127with tendrils 129 is folded into the outer chamber 126. The innerchamber 127 is not inverted in its final position. The tendrils 129expand into the outer chamber 126 providing stability to the final formand baffling characteristics to calm fluid motion in the outer chamber126. The outer chamber 26 membrane remains inverted in its finalposition. A portion of the continuous membrane formed along the fillingtube 121 forms the termination of the membrane. As this portion of themembrane exits the posterior aspect of the implant 113, the surplusmembrane material is trimmed. As in previously described embodiments, aplug 123 is inserted and cured to seal the implant 114. For example, theplug 123 can be formed from viscoelastic material similar to the middlezone 119. The plug 123 functions as a self-sealing injection port thatcan be utilized to pre-fill the outer chamber 126 and inner chamber 127of the implant 114 to a desired volume prior to implantation.Biocompatible thickening agents can also be pre-filled prior to sealingthe implant. This final configuration of the implant 114 has acontinuous viscoelastic membrane forming two self-sealing independentchambers, namely an outer chamber 126 and an inner chamber 127. Theimplant 114 is filled or partially filled with a fluid, such as saline,prior to implantation to a patient.

Exemplary Implant Filled With a Cohesive Gel

In another preferred and non-limiting embodiment or aspect of theinvention, with reference to FIG. 31, an implant 210 includes a cohesivegel 212 enclosed in an elastomeric shell or membrane 214. The gel can beinserted into the membrane or shell in a flowable state and cured toimpart cohesive properties to the implant 210. An example of a cohesivegel 212 that can be used with the implant 210 is a cross-linked dimethylsilicone gel. The membrane 214 can be any of the membranes discussedherein including, for example, a membrane with intrinsic compression(e.g., the two-zone membrane or a three-zone membrane discussed herein),a membrane without intrinsic compression, and/or a pre-stressedmembrane. Desirably, the elastomeric shell or membrane 214 exerts acontracting force on the cohesive gel 212 which is balanced by outwardlydirected forces of the gel 212 to form a stable implant structure. As inpreviously described examples, the shell or membrane 214 is formed froma plurality of laminated layers of an elastomeric material, such assilicone. One or more of the layers can be continuous layers whichentirely enclose the gel 212.

In a preferred and non-limiting example, the elastomeric shell ormembrane 214 is a single zone membrane without intrinsic compression.The shell or membrane 214 can be between about 0.75 mm to 5.0 mm thick,preferably between 1.0 mm and 3.0 mm thick, and more preferably between1.8 mm and 2.5 mm thick. However, shells having a thickness of greaterthan 5.0 mm may be used for particular applications. Layers of theelastomeric shell or membrane 214 can have a Shore hardness of aboutShore 00-10 to Shore A-40.

In a single-zone membrane without intrinsic compression, all of thelayers of the shell or membrane 214 are formed around a single mandrel(e.g., for drip casting) or in a single mold (e.g., using the reversecasting method). Thus, unlike in previously-described embodiments, themembrane 214 may not have intrinsic compression. For example, outer orinner layers or zones of the membrane 214 may not exert contractingforces on middle layers or zones of the membrane 214, as occurs in othermembranes and shells discussed herein. Instead, the elastomeric membrane214 is configured to exert a contracting force on the gel 212. As aresult, a volume enclosed by the elastomeric membrane 214 when cured issmaller than the volume of the gel 212. The volume enclosed by themembrane 214 when cured is also smaller than a volume of the finishedimplant 210, such that in a finished state, the elastomeric membrane 214exerts the contracting force to the gel 212. For example, the volumeenclosed by the shell or membrane 214 when cured may be about 50% to95%, and preferably about 80%, of the volume of the finished implant210. In order to obtain such balanced compression, the volume of theelastomeric shell or membrane 214 when formed can be expanded by about5% to about 50% and preferably about 20% prior to providing the gel 214to the interior of the implant 210.

In some examples, the shell or membrane 214 is formed from simple layersof uniform hardness. In other preferred and non-limiting embodiments oraspects, the membrane 214 may be formed from multiple layers of variablehardness. For example, the layers may decrease in hardness from theoutermost layers towards an inner surface 216 of the membrane 214. Inthat case, the innermost layers of the membrane 214 would be soft.Softer layers have properties which are more similar to the propertiesof the cohesive gel 212. Silicone materials bond better with layershaving similar properties (e.g., hardness), such that that a membrane214 with softer innermost layers bonds more securely with the cohesivegel 212. Accordingly, the membrane 214 can be designed so that thelayers transition slowly to a soft state similar to the gel 212 toensure superior bonding. In some instances, innermost layers of themembrane 214 can include layers with some gel-like properties. In someexamples, outermost layers of the membrane can be a hardness of aboutShore A-20 to Shore A-40 Shore. Innermost layers of the membrane canhave a hardness of about Shore 00-10 to Shore A-20.

In some examples, the gel 212 is a cohesive gel having form stable orsubstantially form stable properties. For example, the gel 212 can be asilicone gel which can be cured by applying heat to the filled implant210. Exemplary gel materials that can be used to fill a cohesive gelimplant are described, for example, in U.S. Pat. No. 4,455,691, entitled“Silicone gel filled prosthesis” and in U.S. Pat. No. 8,858,630,entitled “Variable cohesive gel form-stable breast implant”, each ofwhich is incorporated by reference in its entirety. Other soft polymermaterials may also be used for the gel 212 including, for example,polyesters, polyacrylamides, and others. Exemplary materials aredescribed in U.S. Pat. No. 5,941,909, entitled “Filling material forsoft tissue implant prostheses and implants made therewith”, which isincorporated by reference in its entirety.

An exemplary method for forming a gel filled elastomeric implant 210including a single-zone membrane 214 without intrinsic compression isshown in FIGS. 32A-32E. FIGS. 32A-32C show steps for producing asingle-zone elastomer shell or membrane 214 by the reverse castingmethod discussed herein. In other examples, the single zone shell ormembrane may be formed by drip casting over a mandrel as discussedhereinabove.

As shown in FIG. 32A, a mold 218 is provided. The mold 218 can besimilar in form to molds discussed hereinabove in connection with thereverse casting processing for the multi-zone membrane. In someexamples, the mold 218 may define an inner cavity that is the same shapeas the finished implant, but smaller. For example, the volume of thecavity of the mold 218 may be between 50% and 95%, and preferably about80%, of the volume of the finished implant. When the mold 218 is thesame shape as the finished implant, the membrane expands equally anduniformly to conform to the shape of the finished implant. In otherexamples, the mold 218 may be a different shape than the finishedimplant. For example, the mold 218 may define a simple round form oranother form that is capable of expanding into the shape of the finishedimplant. In some examples, the shape of the mold 218 may be selectedsuch that, when expanded, the membrane produces variable contractileforces against the soft gel. For example, top and bottom portions of themembrane may be configured to exert increased contractile forces on thegel, such that equatorial portions of the finished implant bulge or haveincreased resiliency.

The mold 218 can include a textured interior surface 220 for producing atextured implant. The mold 218 can be a flexible and disposable singleuse product. In other examples, multi-use molds formed from more rigidmaterials can also be used within the scope of the present disclosure.As shown in FIG. 32B, a flowable elastomeric material, such as silicone,is injected or poured into the mold 218 to form an outermost layer ofthe shell or membrane 214. For example, the elastomeric material may bepoured into the mold 218 through a narrow opening 222. The elastomericmaterial can be dispersed on the textured surface 220 of the mold 218 byoscillating or rotating the mold 218. The deposited elastomeric materialdries or becomes form stable. The process can then be repeated multipletimes to deposit multiple layers on the inner surface of the mold. Asdiscussed herein, the hardness of the layers can be modified to producea membrane 214 of variable hardness. For example, the inner most layersof the membrane 214 may be softer than the outermost layers of themembrane 214. Once the multiple layers of elastomeric material aredeposited on the interior surface 220 of the mold 218, the elastomericmaterial can be cured or partially cured to form the single-zone shellor membrane 214. As previously described, the process of depositing andcuring the elastomer material can be carried on multiple times toproduce a laminated multi-layer shell. In some examples, the cured shellor membrane 214 remains open, as shown in FIG. 32B, so that the implantcan be filled by pouring gel through the opening. In other examples, theshell or membrane 214 can be closed to form a continuous membrane. Acontinuous membrane can be stronger and less prone to leaks thanmembranes having an opening covered by a patch or plug.

As shown in FIG. 32C, after being cured or partially cured, thesingle-zone shell or membrane 214 is removed from the mold. In othercases, the shell or membrane 214 can be formed by drip casting on amandrel as described hereinabove.

As shown in FIG. 32D, the shell or membrane 214 is expanded to afinished shape. For example, as shown in FIG. 32D, the membrane 214 canbe placed in a vacuum chamber mold 224 having a rigid-set form defininga cavity with the desired shape of the implant. The vacuum chamber mold224 is actuated, thereby causing the shell or membrane 214 to expand toan enlarged volume and to assume the shape of the mold cavity. Forexample, a valve 226 can be opened and a pump can be engaged to evacuateair from the mold 224 to create a negative pressure in the mold 224.

In other preferred and non-limiting embodiments or aspects, the membrane214 can be expanded by pressurizing the inner cavity or volume of themembrane 214 rather than by application of vacuum force. For example, anopening 228 of the membrane 214 can be connected to a pump or device toinflate the membrane 214. As the membrane 214 inflates, it can bepressed against a mold, thereby causing the membrane 214 to conform tothe shape of the mold. In some preferred and non-limiting embodiments oraspects, expanding the shell or membrane 214 involves expanding aninterior volume of the shell or membrane 214 by about 5% to about 50%prior to filling the shell or membrane 214 with the cohesive gel 212. Inone preferred embodiment, the shell or membrane 214 is expanded by about20% prior to filling the membrane 214 with the cohesive gel 212. It isnoted that for embodiments including the cohesive gel 212, the degree ofexpansion of the shell or membrane 214 is generally less than is neededfor forming a multi-zone membrane with intrinsic compression as show anddescribed in connection with FIGS. 6-15. Further, in some embodiments,the degree of expansion of the shell or membrane 214 is selected suchthat, once vacuum force is removed, the formed implant 210 returns to asize which is slightly larger than the membrane 214 when formed. Forexample, in its completed state, the membrane 214 may enclose a volumewhich is preferably between about 10% and 40% larger than the volumeenclosed by the membrane 214 when originally formed.

As shown in FIG. 32E, while the vacuum pump remains active and the shellor membrane 214 remains in its expanded state, the shell or membrane 214is filled with a filling material, such as a flowable cohesive gel 212.For example, the flowable gel can be poured through the opening 228.After the membrane 214 is filled to a desired volume, the opening 228can be closed or covered, for example, by folding overlapping portionsof the shell or membrane 214 against each other to enclose the gel 212.In other examples, an elastomeric plug may be placed in the opening 228to enclose the gel 212.

If the membrane 214 is an enclosed continuous membrane, the implant canbe filled by injection. For example, an injection needle can be insertedthrough the membrane 214. A second needle for evacuating air from themembrane 214 can be inserted through another portion of the membrane214. Once the needles are in place, fluid, such as the flowable cohesivegel, can be injected into the implant. As the filling material entersthe implant, air is evacuated through the second needle.

Once the membrane 214 is closed, the flowable gel 212 can be curedthereby causing the gel 212 to transition to a form-stable, cohesivestate. For example, the gel 212 can be cured by applying heat to the gel212 and membrane 214. In some examples, the curing temperature forcohesive gel is between about 110° C. and 170° C. In other examples,curing may be initiated using other common techniques, such asapplication of electromagnetic radiation, UV radiation, or by adding acuring agent to the flowable gel material. Curing the gel 212 alsoeffectively bonds the gel 212 to the innermost layers of the membrane214. As discussed herein, in some examples, innermost layers of themembrane 214 can have soft, gel-like properties to improve the bondbetween the gel 212 and membrane 214.

The finished implant 210 generally has the shape of the vacuum chambermold 224. Further, since the shell or membrane 214 is expanded whilebeing filled with the cohesive gel 212, the shell or membrane 214 exertsthe contracting force against the gel 212. Once cured, the form-stable,cohesive structure of the gel 212 counteracts the contracting force,thereby contributing to the resiliency and softness of the finishedimplant.

Exemplary Implants Formed From Preformed Shells

With reference to FIGS. 33A-35B, according to another preferred andnon-limiting embodiment or aspect of the disclosure, a multi-zoneimplant, such as a two zone implant 310 or a three zone implant 410, canbe formed from a preformed elastomeric shell 312, 412, such as apreformed elastomeric shell 312, 412 used in production of conventionalcommercially available implants. In these embodiments, the preformedshell 312, 412 is used in place of the outer zone of previousembodiments to provide support or structure for the implant. Suchpreformed shells 312, 412 are generally formed around a mandrel andcomprise multiple laminated layers of an elastomeric material, such assilicone. The preformed shell 312, 412 are generally less than 1.5 mmthick, or preferably from about 0.25 mm to 1.0 mm thick. Layers of theelastomeric shell or membrane can have a Shore hardness of about ShoreA-20 to Shore A-40. The preformed shell can enclose an interior volumeof about 80 cc to 800 cc.

The preformed shell 312, 412 generally includes only a single zone ofelastomeric layers, meaning that all of the layers of the shell 312, 412are formed around the same mandrel or in the same mold. When forming thepreformed shell 312, 412, a volume of the mandrel or mold used to formthe preformed shell does not change as the layers are formed and cured,as occurs in other methods of forming an implant shell disclosed herein.Instead, the elastomeric layers are applied over top of one another onthe mandrel or mold and permitted to cure to form the shell. Single-zonepreformed shells, which can be used to form the implant disclosedherein, are available commercially from manufacturers including, forexample: Mentor Worldwide LLC of Irvine, Tex.; Allergan PCL of Madison,N.J.; Sientra, Inc. of Santa Barbara, Calif.; and Polytech Health &Aesthetics GmbH of Dieburg, Germany.

Method of Forming a Two-Zone Implant From a Preformed Shell

In some preferred and non-limiting aspects or embodiments, a method offorming an implant 310 for volumetrically altering, replacing,expanding, or augmenting body tissues from the preformed shell 312includes providing the preformed shell 312. In its finished form, theshell 312 includes a two-zone elastomeric membrane having an innersurface 330 and an outer surface 336. As shown in FIG. 33A, thepreformed shell 312 has an inner surface 314 partially enclosing aninterior volume 316, an outer surface 318, and an opening 320 foraccessing the interior volume. The opening 320 is generally about 2.5 cmto 4.5 cm in diameter, though many different sized openings can be usedwithin the scope of the present disclosure. The preformed shell 312 canbe formed from at least one cured elastomeric layer or from a pluralityof laminated elastomeric layers. As shown in FIG. 33B, the methodincludes inverting the preformed shell 312 and expanding the interiorvolume 316 of the inverted preformed shell 312 to an expanded volume, inwhich the interior volume of the shell 312 is greater than a volume ofthe preformed shell 312 at a time of forming the shell 312. For example,expanding the shell 312 may include expanding the interior volume of theshell by between 50% and 800%, preferably about 500%, compared to thevolume of the shell 312 at the time of forming the shell 312. As inpreviously described examples, a volume of the elastomeric shell 312 canbe expanded using a mandrel or mold. For example, the inverted shell 312can be placed over a mandrel 322, such that the outer surface 318 of thepreformed shell 312 contacts the mandrel 322, to place the shell 312 inan expanded state.

After the preformed shell 312 is placed on the mandrel 322, as shown inFIG. 33C, an inner zone 324 including at least one inner elastomericlayer is formed on the inner surface 314 of the shell 312, while theshell 312 is in the expanded state. For example, one or more layers ofthe elastomeric material, such as silicone, can be formed on top of oneanother to form the inner zone 324. Generally, elastomeric layers areformed by either spraying or applying the silicone material to a surfaceand permitting the applied layers to cure. In some examples, theelastomeric layers of the inner zone 324 are softer than layers of thepreformed shell 312. For example, layers of the inner zone 324 can havea Shore hardness from about Shore 00-10 to about Shore A-20 and, forexample, can be formed by blending Shore 00-10 and Shore A-20 materialsto form the inner zone 324. The inner zone 324 may be from about 0.2 mmto about 3.5 mm thick. In that case, the completed two-zone elastomericmembrane has a total thickness of about 0.7 mm to about 4.5 mm

In some examples, the elastomeric layers of the inner zone 324 aresubstantially similar in material composition. In other examples,material properties of the different layers can vary to produce an innerzone 324 with variable hardness and/or elasticity. For example, aproximal-most layer 326 of the inner zone 324 (e.g., a layer of theinner zone 324 nearest to the preformed shell 312) and distal-mostlayers 328 (e.g., layers farthest from the preformed shell 312, whichform an inner surface 330 of the implant 310) can be formed from firmermaterials, such as from a blend of an amount of Shore 00-10 and ShoreA-20 materials. In some examples, firmer layers may make up about 10% to20% of a total volume of the inner zone 324. Interior layers of theinner zone 324 can be blended (e.g., a blend of Shore A-10 elastomer andShore 00-10 elastomer), becoming progressively softer moving towards amiddle of the inner zone 324. Layers near a middle of the inner zone canbe soft. For example, middle layers near the middle of the inner zone324 can have a hardness of Shore 00-10. In general, the blended andsofter layers of the inner zone 324 can make up about 80% to 90% of thetotal volume of the inner zone 324.

As shown in FIG. 33D, after the layers of the inner zone 324 cure, theshell 312 (which can be referred to as a multi-zone shell, since itincludes both the preformed shell 312 and inner zone 324) is removedfrom the mandrel 322 and inverted back to its original orientation. Onceremoved from the mandrel 322, the shell 312 naturally retracts to asmaller volume, closer to the volume of the preformed shell 312 whenoriginally formed (as shown in FIG. 33A). In this retracted position,the pre-formed shell 312 exerts a contracting force on the elastomericlayer(s) of the inner zone 324. Since the layers of the inner zone 324are formed when the preformed shell 312 is in the expanded state,contracting the inner zone 324 compresses layers of the inner zone 324.Such compression causes the layers of the inner zone 324 to fold,creating texturing or a textured region having ridges, grooves, andcrevices on the inner surface 330 of the implant 310. FIG. 33E shows anexpanded view of the shell 312 including the texturing on the innersurface 330 of the implant 310.

After the shell 312 is inverted and retracts to about its originalvolume, a completed implant can be formed. In order to form thecompleted implant, as shown in FIG. 33D, the shell 312 is enclosed toform at least one chamber, in a similar manner as in previousembodiments. For example, a piece of elastomeric material, such as aplug or patch 332, can be vulcanized to the outer surface 336 and/or,preferably, to the inner surface 330 of the shell 312 to cover theopening 320 to fully enclose the interior volume 316 of the implant 310.In some examples, forming the implant 310 can also include filling theimplant 310 with a fluid, such as saline solution or a cohesive gel 334.When a cohesive gel 334 is used as a filling material, in an uncuredstate, the gel 334 can be sufficiently fluid to flow into the ridges,grooves, and crevices on the textured inner surface 330 of the implant310. As the gel 334 cures, it adheres to the textured inner surface 330,which creates a more stable interface between the gel 334 and the layersof the inner zone 324 than if texturing were not present. Specifically,since the textured inner surface 330 has more surface area than a flatsurface enclosing a similar volume, the cohesive gel 334 is better ableto adhere to the inner surface 330, than if texturing were not present.As a result of the stable interface, mechanical properties of the shell312 and implant 310 are improved. For example, as a result of adhesionbetween the gel 334 and textured inner surface 330, a likelihood ofdelamination of the gel 334 and inner surface 330 of the shell 312 isreduced. Accordingly, the formed implant 310 is better able to maintainits shape, giving the completed implant 310 a more natural appearanceand feel. Delamination of the shell 312 and gel 334 can also occur whenthere is a substantial difference in material properties between theinner surface 330 of the shell and the gel 334. Therefore, it isdesirable that the distal-most layers 328 of the inner zone 324 are amore similar in hardness to the cohesive gel 334 than are layers of thepre-formed portion of the shell 312.

Method of Forming a Three-Zone Implant From a Preformed Shell

According to another preferred and non-limiting aspect or embodiment ofthe present disclosure, steps for forming the three-zone implant 410from a preformed shell 412 including an elastomeric membrane having atextured inner surface 430 and a textured outer surface 436 are shown inFIGS. 34A-34D. In order to form the implant 410, as in the previousexample, a commercially available preformed shell 412 is provided, asshown in FIG. 34A, and transformed to an expanded state, as shown inFIG. 34B. For example, the preformed shell 412 can be placed over amandrel 422, such that an inner surface 414 of the shell 412 contactsthe mandrel 422. With the shell 412 in the expanded state, as shown inFIG. 34C, an outer zone 440 including at least one outer elastomericlayer is formed on at least a portion of an outer surface 418 of thepreformed shell 412. For example, as in previous embodiments, aplurality of layers of elastomeric material can be deposited on thesurface 418 of the shell 412 and laminated to form the outer zone 440 ofelastomeric layers. In general, layers of the outer zone 440 are firmerthan layers of the inner zone 324 (shown in FIGS. 33A-33E). For example,layers of the outer zone 440 may have a hardness of from Shore 00-30 toShore A-20. The outer zone 440 can be from about 0.1 mm to about 1.0 mmthick. In that case, a shell of the three-zone implant 410 can have atotal thickness of from about 0.8 mm to 5.0 mm In some examples, thelayers of the outer zone 440 are formed from materials having differingmaterial properties. For example, a proximal-most layer 442 (e.g., alayer closed to the preformed shell 412) and a distal-most layer 444(e.g., the layer farthest from the preformed shell 412) may be formedform firmer materials, while layers in a middle of the outer zone 440can be softer.

After the layers of the outer zone 440 cure, the shell 412 (which can bereferred to as a multi-zone shell, since it includes the preformed shell412 and outer zone 440) can be removed from the mandrel 422 or mold andinverted, such that the inner surface 430 of the implant 410 facesoutward. The shell 412 is then expanded again either using a mold or byplacing the shell on a mandrel 422 in the inverted orientation, suchthat the outer surface 436 of the implant 410 contacts the mandrel 422.Once the shell 412 is mounted to the mandrel 422 in its invertedorientation, as shown in FIG. 34D, an inner zone 424 including at leastone inner elastomeric layer can be formed by applying elastomeric layersto the shell 412. The mandrel 422 used for forming the inner zone 424has a volume that is greater than a volume enclosed by the preformedshell 412 at the time of forming the shell 412. In some examples, themandrel 422 used for forming the inner zone 424 is the same as themandrel 422 used for forming the outer zone 440. In other examples, themandrels 422 used for forming the inner zone 424 and the outer zone 440may be different volumes to vary the compression or contraction forcesapplied to the zones 424, 440 by the preformed shell 412. As in theprevious example, the inner zone 424 can include a plurality ofelastomeric layers having the same hardness or varying hardness.Generally, the inner zone 424 is softer than the outer zone 440 or thepreformed shell 412. For example, the layers of the inner zone 424 canhave a hardness of from about Shore 00-10 to about Shore A-20.

After the inner zone 424 is formed, the shell 412 (which is a multi-zoneshell with three distinct zones) is removed from the mandrel 422 andinverted back to its original position, as shown in FIG. 34A. Removingthe shell 412 from the mandrel 422 allows the shell 412 to retract to avolume closer to a volume of the preformed shell 412 when formed. Inthis orientation, the preformed shell 412 exerts a retracting force onlayers of the outer zone 440 and compresses layers of the inner zone424, thereby causing the shell 412 to adopt a volume less than a volumeof the mandrel 422. The retraction of the layers of the outer zone 440and compression of layers of the inner zone 424 causes the layers of theinner zone 424 and the outer zone 440 to fold upon one another, therebyproducing textured regions on the inner surface 430 and the outersurface 436 of the implant 410. A detailed cross-sectional view of theshell 412 including the textured inner and outer surfaces 430, 436 isshown in FIG. 35B.

Once the shell 412 is completed, the implant 410 is formed by enclosingthe shell 412 to form at least one chamber. For example, as in previousexamples, the opening 420 of the shell 412 can be enclosed by attachingand/or vulcanizing a piece of elastomeric material, such as a plug orpatch 432, to the outer surface 436 and/or, preferably to the innersurface 430 of the shell 412, to form a secure seal covering the opening420. As in previous examples, the chamber of the implant can be filledwith a liquid, such as saline, or with a cohesive gel 434 which, whencured, adheres to the textured inner surface 430 of the inner zone 424.As previously described, adhesion between the shell 412 and the cohesivegel 434 is enhanced as a result of the increased surface area of thetextured inner surface 430 compared to a flat surface enclosing the samevolume.

The completed three-zone implant 410 is shown in FIGS. 35A and 35B. Theimplant 410 includes the enclosed or partially enclosed elastomericshell 412 and the cohesive gel 434 disposed in an interior of theelastomeric shell 412. As in previous examples, the cohesive gel 434adheres to the textured inner surface 430 of the shell 412 to provide astable interface between the shell 412 and gel 434, which reduces apossibility of delamination. The elastomeric shell 412 includes thepre-formed portion or shell 412 comprising at least one elastomericlayer. The elastomeric shell 412 also includes the outer zone 440 andinner zone 424. As described above, in the completed implant 410, layersof the outer zone 440 and the inner zone 424 are forced to conform to areduced volume, which is less than a volume enclosed by the inner zone424 and/or the outer zone 440 when cured. As a result of the retractionof the outer zone 440 and compression of the inner zone 424, the innersurface 430 and the outer surface 436 of the implant shell 412 aretextured. The textured surfaces 430, 436 are shown, for example, in FIG.35B and in the photographs of FIGS. 36A and 36B. The cohesive gel 434 isconfigured to adhere to the textured surface 430 of the inner zone 424to form a stable interface between the cohesive gel 434 and inner zone424. In a similar manner, the textured outer surface 436 providesenhanced adhesion between the implant 410 and biological tissues, suchas breast tissues, which can improve surgical outcomes. For example, asa result of the textured outer surface 436, the implant 410 can be moresecurely anchored within biological tissue.

Surfaces having different degrees of texturing, such as different sizesof folds or depths of crevices, can be formed by using materials ofdiffering hardness and/or based on an amount of retraction andcompression of the layers. While many different arrangements arepossible, generally, the softer inner zone 434 will have larger folds,to provide additional surface area for promoting adhesion between thecohesive gel 434 and inner surface 430 of the shell 412. A photograph ofan exemplary inner surface 430 including large folds is shown in FIG.36A. Generally, the textured surface 436 of the outer zone 440 has amore granular appearance with a larger number of smaller folds. Aphotograph of an exemplary outer surface 436 is shown in FIG. 36B.

Although the invention has been described in detail for the purpose ofillustration based on what is currently considered to be the mostpractical and preferred embodiments, it is to be understood that suchdetail is solely for that purpose and that the invention is not limitedto the disclosed embodiments, but, on the contrary, is intended to covermodifications and equivalent arrangements. For example, it is to beunderstood that the present invention contemplates that, to the extentpossible, one or more features of any embodiment can be combined withone or more features of any other embodiment.

The invention claimed is:
 1. A method of forming an implant forvolumetrically altering, replacing, expanding, or augmenting bodytissues, the method comprising: providing a preformed shell formed fromat least one cured elastomeric layer, the preformed shell comprising anouter surface, an inner surface, and an opening for accessing aninterior volume of the preformed shell; expanding the preformed shell toan expanded state, in which the interior volume is greater than theinterior volume of the preformed shell at a time of forming thepreformed shell; forming an inner zone comprising at least one innerelastomeric layer on at least a portion of the inner surface of thepreformed shell, while the shell is in the expanded state, therebyforming a multi-zone shell; reducing the interior volume of themulti-zone shell, thereby contracting the at least one inner elastomericlayer of the inner zone and causing texturing of the at least one innerelastomeric layer; and forming the implant by enclosing the multi-zoneshell to form at least one chamber.
 2. The method of claim 1, whereinexpanding the preformed shell to the expanded state comprises invertingthe preformed shell and placing the inverted preformed shell on amandrel, such that the outer surface of the shell contacts a surface ofthe mandrel.
 3. The method of claim 2, wherein a volume enclosed by thesurface of the mandrel is greater than the interior volume of thepreformed shell at the time of forming the preformed shell.
 4. Themethod of claim 2, wherein reducing the interior volume of themulti-zone shell comprises removing the multi-zone shell from themandrel and returning the multi-zone shell to a non-invertedorientation.
 5. The method of claim 1, wherein expanding the preformedshell comprises expanding the interior volume of the preformed shell bybetween 50% and 800% compared to the volume of the preformed shell atthe time of forming the preformed shell.
 6. The method of claim 1,wherein forming the inner zone comprises, while the preformed shell isin the expanded state, forming a plurality of laminated innerelastomeric layers of variable hardness on the inner surface of thepreformed shell.
 7. The method of claim 6, wherein a proximal-most layerof the plurality of inner elastomeric layers and a distal-most layer ofthe plurality of inner elastomeric layers are firmer than middle layersof the plurality of laminated inner elastomeric layers.
 8. The method ofclaim 7, wherein the proximal-most layer and the distal-most layer ofthe plurality of inner elastomeric layers are formed by blendingelastomeric materials having a hardness of up to Shore A-20, and whereinthe middle layers of the plurality of inner elastomeric layers have ahardness of between about Shore 00-10 and Shore A-10.
 9. The method ofclaim 1, wherein forming the implant comprising filling the interiorvolume of the multi-zone shell with a flowable elastomeric material andcuring the flowable elastomeric material to form a cohesive gel.
 10. Themethod of claim 9, wherein the cohesive gel is bonded to the texturingof the at least one inner elastomeric layer.
 11. The method of claim 10,wherein a volume of the cohesive gel when cured is between about 5% and50% larger than a volume enclosed by the preformed shell at the time offorming the preformed shell.
 12. The method of claim 1, furthercomprising forming an outer zone comprising at least one outerelastomeric layer covering at least a portion of the outer surface ofthe preformed shell, while the preformed shell is in the expanded stateand prior to forming the inner zone.
 13. The method of claim 12, furthercomprising reducing the interior volume of the preformed shell afterforming the outer zone, which causes texturing of the at least one outerelastomeric layer of the outer zone.
 14. The method of claim 13, whereinthe texturing of the outer zone is configured to provide an adhesionregion for improving adhesion with surrounding body tissues.
 15. Themethod of claim 12, wherein the outer zone comprises a plurality ofouter elastomeric layers of variable hardness ranging from about Shore00-30 to Shore A-20.
 16. The method of claim 12, wherein forming theouter zone comprises placing the preformed shell on a mandrel, such thatthe inner surface of the preformed shell contacts the surface of themandrel, and applying the at least one outer elastomeric layer to theouter surface of the preformed shell.
 17. The method of claim 16,wherein a volume enclosed by the mandrel is greater than the volume ofthe preformed shell, at the time of forming the preformed shell.
 18. Amethod of forming an implant for volumetrically altering, replacing,expanding, or augmenting body tissues, the method comprising: providinga preformed shell formed from at least one cured elastomeric layer, thepreformed shell comprising an outer surface, an inner surface, and anopening for accessing an interior volume of the preformed shell; placingthe preformed shell on a mandrel to expand the preformed shell to anexpanded state in which the interior volume of the preformed shell isgreater than a volume of the preformed shell at a time of forming thepreformed shell; while the preformed shell is on the mandrel, forming anouter zone comprising at least one outer elastomeric layer on at least aportion of the outer surface of the preformed shell, while the preformedshell is in the expanded state, to form a multi-zone shell; placing themulti-zone shell on the mandrel in an inverted orientation, in which theouter zone of the multi-zone shell contacts the mandrel; forming aninner zone comprising at least one inner elastomeric layer on at least aportion of the inner surface of the multi-zone shell, while themulti-zone shell is on the mandrel and in the expanded state; reducingthe interior volume of the multi-zone shell by removing the multi-zoneshell from the mandrel, thereby contracting the at least one outerelastomeric layer and the at least one inner elastomeric layer, andcausing texturing of the at least one outer elastomeric layer and the atleast one inner elastomeric layer; and forming the implant by enclosingthe shell to form at least one chamber.
 19. An implant forvolumetrically altering, replacing, expanding, or augmenting tissues,comprising: an enclosed or partially enclosed elastomeric shell formedfrom a plurality of laminated elastomeric layers, the elastomeric shelldefining an interior volume; and a cohesive gel disposed in the interiorvolume of the elastomeric shell, wherein the elastomeric shellcomprises: a preformed shell comprising at least one elastomeric layer,the preformed shell having an inner surface and an outer surface; anouter zone comprising at least one outer elastomeric layer covering atleast a portion of the outer surface of the preformed shell; and aninner zone comprising at least one inner elastomeric layer covering atleast a portion of the inner surface of the preformed shell, wherein avolume enclosed by the outer zone and the inner zone at the time offorming the outer zone and the inner zone is greater than a volume ofthe preformed shell at a time of forming the preformed shell.
 20. Theimplant of claim 19, wherein the volume enclosed by the outer zone andthe inner zone of the implant is less than the volume enclosed by theouter zone and the inner zone at the time of forming the outer zone andthe inner zone, such that the preformed shell exerts a contracting forceon the inner zone and the outer zone, which causes texturing of theinner zone and the outer zone.